KR0182778B1 - First-in first-out semiconductor memory device - Google Patents

Abstract

A semiconductor memory device including an address generating means therein, which is used to access a memory cell array in order to improve data transfer efficiency, accurately determine the accumulated data number, and freely set the accumulated data number. Rewrite of the lead address counter for generating the internal lead address signal used for the purpose, the selection means for selecting the bit cell in the memory cell array according to the internal lead address signal supplied from the lead address counter, and enabling the internal read address signal to be rewritten And a first terminal to which a first control signal is supplied.

By using such a device, data transfer efficiency can be improved, the accumulated data number can be grasped accurately, and the accumulated data number can be freely set.

Description

SEMICONDUCTOR MEMORY DEVICE

1A is a block diagram of one embodiment of a receiving side of a communication control apparatus including a FIFO memory according to the present invention.

1B is a block diagram of one embodiment of a transmitting side of a communication control apparatus including a FIFO memory according to the present invention.

2 is a block diagram showing a detailed example for selecting a unit memory area of a received FIFO memory.

3 is a block diagram showing a detailed example for selecting a unit memory area of a transmission FIFO memory.

4 is a logic circuit diagram showing an example of the selection control circuit included in the reception FIFO memory.

5 is a logic circuit diagram showing an example of a selection control circuit included in the transmission FIFO memory.

6A to 6C are explanatory diagrams showing an example of the data lead state from the reception FIFO memory.

7A to C are explanatory diagrams showing an example of the data lead state from the transmission FIFO memory.

8 is a circuit diagram showing an example of a bit cell included in a received FIFO memory.

9 is a circuit diagram showing an example of a bit cell included in a transmission FIFO memory.

FIG. 10 is an explanatory diagram showing an example of the relationship between the count value of the write counter and read counter and the number of accumulated data in the transmission FIFO memory. FIG.

11A to 11C are logic circuit diagrams showing one example of the adder of the calculation unit included in the reception FIFO memory.

12 is a block diagram of an example for calculating the number of accumulated data using a flag.

13 is a block diagram of a FIFO memory, which is another embodiment of the present invention.

FIG. 14 is a block diagram showing an essential part of a processor including the FIFO memory shown in FIG. 13 in one semiconductor substrate. FIG.

15A and 15B are explanatory views showing one example of clear processing in a FIFO memory.

Figure 16 is a block diagram of a FIFO memory, which is another embodiment of the present invention.

FIG. 17 is a block diagram showing an example of a system including the FIFO memory shown in FIG.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a semiconductor memory device including an address generating means therein, in particular a FIFO memory (first-in first-out memory) for temporarily storing data in a first-in, first-out form. It relates to a valid technology applied to the control system.

When transferring data between multiple devices or function modules having different data processing speeds or transfer speeds, a FIFO memory or the like can be used as a buffer memory in order to absorb such different capacities or speeds. For example, in the communication control LSI, a transmission FIFO memory and a reception FIFO memory are disposed between a line control unit for transmitting and receiving data between communication lines and a bus interface unit connected to a host device. The receiving FIFO memory sequentially stores the data received by the circuit control unit, and the accumulated data is sequentially read by the host device via the bus interface unit and used for data transmission or data processing. The transmission FIFO memory sequentially stores transmission data supplied from the host device via the bus interface unit, and the accumulated data is sequentially read by the circuit control unit and used for transmission.

By the way, in the reception FIFO memory and the transmission FIFO memory, data is accumulated by the relationship between the overhead reduction for data transfer between the host system and the data processing capability of the host system, in addition to the prevention of overrun of the received data. The inventors have found the need to freely control the number or further inform the host apparatus of the data accumulation number in real time. At this time, as a technique for obtaining the data accumulation number of the FIFO memory, for example, as described in Japanese Patent Laid-Open No. 62-225050, it is incremented every time a write operation is instructed in the FIFO memory, and a read operation is instructed. There is a technology that uses a dedicated counter that decrements each time.

In addition, since a frame or character in data transmission / reception is usually transmitted with a minimum unit of 8 bits, the conventional transmission FIFO memory and the reception FIFO memory transmit data in units of 8 bits between the circuit control unit. . In the related art, the transmission / reception FIFO memory and the bus interface unit are only connected to one 8-bit bus. An example of the literature described for the bus structure of such a FIFO memory is US Intel Corporation 82586 (published March 1984, LAN Components Users Manual 2. 13).

However, one dedicated counter that is incremented each time to write and decremented every time to obtain the data accumulation number of FIFO memory is used. There is a problem that the creep operation is difficult to execute accurately, and therefore it is difficult to expect accuracy in acquiring the accumulated data number.

In addition, the present inventors have reviewed a technique for requesting transmission of transmission data to the host device according to the accumulated data of the remaining transmission data transferred from the host device to the transmission FIFO memory. Considering only the request for transmission, no consideration has been given to controlling the number of data transferred from the host device to the transmission FIFO memory. For this reason, when a large number of transmission FIFO memories are provided for each channel of a circuit control unit supporting multiple channels, data transmission may be required from a plurality of transmission FIFO memories to an upper device in operation. In the conventional configuration in which the negate condition of the transfer request to the FIFO memory cannot be freely set, there is a concern that the bus is occupied indefinitely for data transfer to the transmission FIFO memory, and other necessary processing by the host apparatus is prevented.

In addition, when the bus interface unit in the communication control device can be connected to the host device via a bus having a bit structure such as 16 bits, data is transmitted between the host device and the bus interface unit in units of 16 bits and transmitted as usual. If the FIFO memory or the receiving FIFO memory and its bus interface are each connected by an 8-bit bus, the data transfer must be executed by dividing the data into several circuits between the transmitting FIFO memory, the receiving FIFO memory and the bus interface. There was a problem that the data transfer efficiency between devices was reduced.

In order to accumulate data in a first-in-first-out format, the FIFO memory is provided with address counters such as read counters and write counters, and the access counter for the memory cell array is instructed by the read counter or the write counter. For example, when the data is empty, the values of the lead counter and the light counter are matched. Whenever the data write operation is instructed, the value of the write counter is incremented. When the data read operation is instructed, the read counter value is increased. It is incremented. An example of a document described for such a FIFO memory is Nikkei Electronics No. 423 (published on June 15, 1987, pp. 181 to 188) issued by Nikkei McGraw-Hill. However, in the conventional FIFO memory, since the order of reading and writing data is uniquely determined by a built-in address counter such as a read counter or a write counter, it cannot respond to any request for random access to the memory cell. For example, if the system needs to check the data stored in the middle of the FIFO memory, it must wait until the required data is output sequentially. In addition, in order to clear the unnecessary data due to an error in the system operation, it is necessary to read all the unnecessary data sequentially and update the read counter value. It was made clear by the present inventors to be the thing which hinders.

An object of the present invention is to provide a FIFO type semiconductor memory device that can improve the data transfer efficiency to the outside.

Another object of the present invention is to provide a FIFO type semiconductor memory device capable of accurately determining the accumulated data number.

Another object of the present invention is to provide a FIFO type semiconductor memory device capable of freely setting the accumulated data number.

Another object of the present invention is to provide a semiconductor memory device which can be randomly accessed even if the order of reading or writing data to and from a memory cell is defined by the built-in address counter.

Still another object of the present invention is to provide a semiconductor memory device which can easily perform data clearing processing even if the order of reading or writing data to and from a memory cell is specified by an internal address counter.

The above and other objects and novel features of the present invention will become apparent from the description and the accompanying drawings.

Brief descriptions of representative ones of the inventions disclosed herein are as follows.

That is, the FIFO memory is formed by connecting the input signal line and the output signal line of the data to each bit cell included in the bit cell array such that the number of parallel lead bits and parallel write bits of the data has an integer multiple of two or more. In the case of accumulating data in units of one bit in a first-in-first-out format, one port of the FIFO memory can receive multiple times of unit data as compared to the other port. Improve the data transfer efficiency with For example, when the FIFO memory is arranged between the circuit control unit and the bus interface unit of the communication control device, the FIFO memory receives the circuit control unit and data in octets, and receives the bus interface unit and data in multiple units. .

At this time, by providing a control circuit for selectively controlling the relationship between the number of parallel lead bits of data and the number of parallel write bits by an integer multiple of the same or two or more, it is versatile for a bus connection configuration between a FIFO memory and a circuit block for performing data transfer. In addition, bus replacement can be easily performed without using an external circuit, and the convenience of using a FIFO memory is improved.

The calculating means for acquiring the accumulated data number of the received FIFO memory includes a comparator means for substantially comparing the value of the light counter with the value of the lead counter, and the value of the light counter and the lead counter according to the comparison result by the comparing means. The accumulated data number is calculated according to the value of and the number of storage stages in the unit memory area. At this time, the lead counter and the light counter operate separately to give each count value to the calculation means, and in this way, the calculation means processes the values separately given by both counters, thereby accumulating the data even if read and write occur. Achieves to get the number correctly.

The lead counter and the ride counter are inverted each time the count value is returned to the initial value, so that both states can be judged by comparing means so that the value of the lead counter and the light counter can be compared. By making it possible to calculate the accumulated data number, it is possible to facilitate the large and small discrimination after the value of the light counter is returned to the initial value sequentially.

When the number of storage stages of the FIFO memory is relatively small, a flag corresponding to one-to-one is provided in the unit memory area, the flag corresponding to the position indicated by the light counter is set, and the flag corresponding to the position indicated by the light counter. By acquiring the control means for controlling the to be in the reset state and the logic gate array for acquiring the accumulated data number of the bit cell array in the state of each flag, the accurate acquisition of the accumulated data number is achieved in the same manner as above.

Although the accumulated data number acquired in this way can be given to the outside as it is, in order to be able to freely set the number of data stored therein using the accumulated data number acquired internally, that is, In order to be able to freely set the timing for instructing data transmission to the outside in relation, the setting value of the register that can arbitrarily set the assertion condition of the transmission ready signal for instructing the data transmission to the outside and the number of accumulated data acquired internally The transmission ready signal may be generated to determine the astiming according to the comparison result.

At this time, if the bus occupancy period by the data transfer of the FIFO memory becomes inconvenient, the negate timing of the transmission ready signal can be freely controlled according to the comparison with the setting value of the register that can arbitrarily set the negate condition of the transmission ready signal. You may also

In this way, a control register that can arbitrarily set the assertion condition of the transmission ready signal is provided, and further, a control register that can arbitrarily set the negate condition, and a comparison between the set value of this register and the number of accumulated data acquired therein. By determining the assert timing or the gate timing of the transmission ready signal according to the result, the number of storage stages of the FIFO memory can be controlled in appearance.

This makes it possible to relatively reduce the number of accumulated data in the FIFO memory when the load of the device processing the data of the FIFO memory is small or to increase the number of accumulated data when the load is large, thereby improving the flexibility of the system operation easily. In addition, the throughput of the system can be easily improved by reducing the frequency of data transfer requests during high-speed operation, that is, by reducing the overhead for activating the data transfer control.

In addition, in the semiconductor memory device in which the order of reading or writing data is defined by the built-in address counter, selection means for selecting the output address signal of the address counter and the address signal supplied from the outside is provided. By employing an external address signal as an access address signal, it is possible to restrain and control the update operation of the address counter, so that necessary data can be obtained from any address other than the address while maintaining the address indicated by the address counter. have. As a result, random access is possible even in the case of a semiconductor memory device whose data is read or written in the order specified by the built-in address counter.

In addition, when unnecessary data is generated in the middle of the stored data by enabling the external address value to be rewritten externally, which prescribes the data read or write order, the address counter is forcibly rewritten externally. It is to achieve a simple execution of the clear processing. In the semiconductor memory device configured as described above, when the address counter value is rewritten when random access or unnecessary data is cleared, it is necessary to know the state of the address counter externally via an external data input / output terminal. It is desirable to allow the value of the address counter to be read externally.

EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention is demonstrated with an Example.

[Communication control device (1)]

The communication control apparatus according to the embodiment of the present invention, in which the configuration of the receiving side is shown in FIG. 1A and the configuration of the transmitting side is shown in FIG. 1B, is not particularly limited. It is formed on one semiconductor substrate.

Although the communication control device 1 is not particularly limited, the reception circuit 2 which receives reception data transmitted in serial bits on the reception line RL and converts them serially or in parallel into octets (8-bit units) or parallel data to be transmitted is octet units. Circuit control unit 4 including a transmission circuit 3 for parallel / serial conversion to a transmission line TL and a bus interface unit 5 for interfacing with the host device. Between the bus interface 5 and the receiving circuit 2, a receiving FIFO memory 6 for temporarily storing received data converted in parallel in order in octets is arranged, and the bus interface 5 and the transmission are arranged. Between the circuits 3, there is provided a transmission FIFO memory 7 which temporarily stores data to be transmitted sequentially in octets. In addition, the unit of serial / parallel conversion in the reply control section 4 is not limited to 8 bits in length, but may be any number of bits as long as it is constant at a finite length. The last train of the serial data string may be the one that fits in the number of unit bits or may remain. The first and last recognition of serial data is performed by the receiving circuit 2 in a predetermined order. Similarly, the transmission circuit 3 adds information for recognizing the beginning or the end of the transmission data. These control orders are determined according to the protocols supported by the communication control device, and the details thereof are not limited.

The bus interface unit 5 is not particularly limited, but the CPU (Central Processing Unit) 9, single addressing, which is in charge of controlling the entire system via a system bus 8 including a 16-bit data bus, an address bus, and the like. Direct Memory Access Controller (DMAC) 10 capable of performing block transfer control of data in dual mode or duplex mode, and Random Access Memory (RAM) 11 used for data storage area and CPU 9 work area. It is coupled to the upper device of. The bus interface unit 5 has a bus control signal output from the bus master module such as the CPU 9 or the DMAC 10 of the host device, for example, a read / write signal R / W indicating a data transfer direction, and a system bus ( 8) Data strobe signal DS indicating that the data on the data bus included in the data is valid, bus high signal BH indicating that the upper 8 bits of the 16-bit data bus are valid, and indicating that the lower 8 bits of the 16-bit data bus are valid. The buslow signal BL is supplied.

When the reception circuit 2 receives data, the reception data is sequentially written to the reception FIFO memory 6. When the number of accumulated data in the reception FIFO memory 6 reaches a predetermined number, the reception FIFO memory 6 sends a ready signal for instructing the host apparatus to read access the reception FIFO memory 6, for example, a DMA transmission tool signal DREQ1. Is asserted to a predetermined channel of the DMAC 10. On the other hand, the DMAC 10 transfer-controls the retrofit data of the reception FIFO memory 6 to the RAM 11 in the mutual address mode. The transferred data from the RAM 11 is used for predetermined protocol processing by the CPU 9 and the like.

The transmitting circuit 3 sequentially transmits the data stored in the transmitting FIFO memory 7 in a predetermined order, but when the number of data remaining in the transmitting FIFO memory 7 decreases, the transmitting FIFO memory 7 moves to the host apparatus. A transmission ready signal for indicating the write of data to be transmitted, for example, the DMA transmission request signal DREQ2, is asserted to a predetermined channel of the DMAC 10. As a result, the DMAC 10 transfers and controls the data to be transmitted stored in the RAM 11 to the transmission FIFO memory 7 in the single addressing mode.

The various control registers built in the communication control device 1 are not particularly limited, but are directly accessible by the CPU 9. That is, when an address signal is supplied from the CPU 9 to the bus interface unit 5, a register selecting circuit that decodes the address signal selects a register corresponding to this address, and thus the CPU 9 for the selected register. Executes initial setting of control data.

[Receive FIFO Memory (6)]

Although the receiving FIFO memory 6 is not particularly limited, the bit cell array 13 including a plurality of unit memory areas RE _{0 to} RE _m having 8 bit cells for one unit, selection control of the unit memory area, and the like. The DMA transfer request signal DREQ1 by using the FIFO control unit 14 for executing the operation, the operation unit 15 for calculating the number of data stored in the bit cell array 13, and the accumulated data number acquired by the operation unit 15. And a transmission preparation generating unit 16 to generate.

The bit cell array 13 is not particularly limited but is formed by arranging the bit cells BC in n rows and 8 columns as shown in FIG. 2, and each of the 8 bit cells in each row is 8 bits of unit memory area RE. constitute ₀ ~RE _m.

The designation of the unit memory area in the data write operation to the bit cell array 13 is executed by the write counter 20, and the unit of the unit memory area is obtained by the write address decoder 21 decoding the coefficient data RCOUNTw. Is selected. The designation of the unit memory area in the data read operation is performed by the read counter 22, and the predetermined unit memory area is selected by the read address decoder 23 decoding the coefficient data RCOUNTr. In the initial state of the receiving FIFO memory 6, the values of the light counter 20 and the read counter 22 are initialized to zero.

(Receive FIFO Memory (6) ... Light Counter (20))

The light counter 20 instructs the position of the first unit memory area to be written, and the information is output toward the write address decoder 21. When the reception data is output from the reception circuit 2 to the bit cell array 13, the reception circuit 2 asserts the strobe signal RWS accordingly. When the strobe signal RWs passes through the gate 25, the write address decoder 21 decodes the value of the light counter 20 in synchronization with the assertion of the strobe signal RWs to select a unit memory area, The reception data is written to the unit memory area. Subsequently, the light counter 20 is incremented in synchronism with the negate timing of the strobe signal RWS, whereby the light counter 20 holds the next write position.

Further, in the full state in which the data before reading all the unit memory areas RE _{0 to} RE _m is written, that is, the accumulated data number of the bit cell array 13 is equal to the number of unit memory areas (number of storage stages). New reception data cannot be written. In this state, a full state detection circuit 26 for determining whether the bit cell array 13 is in a full state by receiving the accumulated data number calculated by the operation unit 15 is provided to stop the write. The RFS is applied to the gate 25 so that the strobe signal RWS is not transmitted to the light counter 20 and the light address decoder 21 when in the full state.

(Receive FIFO Memory (6) ... Lead Counter (22))

The lead counter 22 instructs the position of the leading unit memory area to be read, and the information is output toward the lead address decoder 23. When the read operation of the receiving FIFO memory 6 is instructed by the data strobe signal DS, the read / write signal R / W, the bus low signal BL, and the bus high signal BH output from the host device, the bus interface unit 5 reads the read / write signal. When the write signal R / W is at the read operation instruction level equal to the high level, the strobe signal RRS is asserted in synchronization with the timing at which the data strobe signal DS is asserted to the high level. In synchronization with this assertion timing, the read address decoder 23 decodes the value of the read counter 22, and the reception data is read in the unit memory area. Then, in synchronization with the gate timing of the strobe signal, the counter controller 27 increments the lead counter 22, whereby the lead counter 22 holds the next lead position. Incremental operation of the lead counter by the counter controller 27 is determined by the state signals LDS and HDS according to the levels of the bus low signal BL and the bus high signal BH. That is, when both the bus low signal BL and the bus high signal BH are asserted to the high level and both status signals LDS and HDS are at the high level, that is, both the lower 8 bits and the upper 8 bits of the 16-bit data bus are used. In the state in which data transfer is instructed, the counter controller 27 increments (counts up) the read counter 22 twice using the count clocks RRC1 and RRC2. This is because two unit memory areas are selected at the same time when data is read in units of 16 bits by the host device. In addition, when only one of the bus low signal BL and the bus high signal BH is asserted, i.e., instructing to perform data transfer using either the lower 8 bits or the upper 8 bits of the 16-bit data bus. The counter controller 27 increments (1 counts up) the lead counter once using either the count clock RRC1 or RRC2.

In the empty state in which all the data stored in the unit memory areas E _{0 to} E _m are read, that is, when the accumulated data number of the bit cell array 13 is zero, there is no information to be read anymore. In this state, an empty state detection circuit 29 is provided which determines whether or not the bit cell array 13 is empty by receiving the accumulated data number calculated by the calculating unit 15 to prevent reads. The detection result signal RES is applied to the read address decoder 23 and the counter controller 27 so that the change in the strobe signal RRS is ignored.

[Receive FIFO memory (6) ... 2 byte parallel lead]

Each bit cell BC is not particularly limited in order to read two received data in units of one byte (8 bits) in parallel in the bit cell array 13, but as shown in FIG. One write data line Dwi (i = 0 to 7) is coupled to the data input terminal D of the latch circuit 30 via the select switch 31, and the select switch is respectively connected to the data output terminal Q of the latch circuit 30. The upper lead data line HDri and the lower lead data line LDri are connected in common through (32) and (33). The select terminal of the select switch 31 is coupled to the write word line Wwj (j = o to m), and the select terminals of the select switches 32 and 33 are the upper lead word line HWrj and the lower lead weed line LWrj X. Each is connected. As shown in FIG. 2, the write word line Wwj, the upper lead word HWrj, and the lower lead word line LWrj are commonly connected to one row and eight bit cells BC constituting one unit storage area, and the write data line Dwi. The upper lead data line HDri and the lower lead data line LDri are commonly connected to n bit cells BC in one column.

The write data lines Dw0 to Dw7 are coupled to the data output terminal of the reception circuit 2 via the 8-bit internal bus 35 shown in FIG. The lower lead data lines LDr0 to LDr7 pass through the 8-bit internal bus 37 shown in FIG. 1a, and the upper lead data lines HDr0 to HDr7 pass through the 8-bit internal bus 37, respectively. Is connected to the lower 8 bits and the upper 8 bits of the 16-bit data bus of the system bus 8, respectively.

The light word lines Ww0 to Wwm are sequentially connected to the output terminals of the write address decoder 21 which decodes the coefficient value provided by the light counter 20 to form the selection signals RSw0 to RSwm. According to the decoding result of the given coefficient value, a predetermined one is controlled at a selection level such as a high level. When one write word line Wwj becomes the selection level, the 8-bit reception data provided in the write data lines Dw0 to Dwm is written to the unit memory area Ej consisting of one row and eight bit cells BC connected thereto. The write timing is determined in accordance with the clock change or level of the signal supplied to the clock input terminal CK of the latch circuit 30. For example, the signal of the write word line Wwj may be applied to the clock input terminal CK as it is.

The selection operation of the lower lead word lines LWr0 to LWrm and the upper lead word lines HWr0 to HWrm is executed by the selection control circuit 40 which receives the selection signals RSr0 to RSrm output from the read address decoder 23. The lead address decoder 23 sets one of the selection signals RSr0 to RSrm to the same selection level as the high level in accordance with the decoding result of the coefficient value provided by the read counter 22.

The selection control circuit 40 controls two bytes of data in parallel reading by one selection operation by the read address decoder 23, so that the selector RSEL ₀ to RE provided for each unit memory area RE _{0 to} RE _m . It consists of RSEL _m .

The selectors RSEL _{0 to} RSEL _m include logic gates identical to each other. For example, the selector RSELj has two inputs of a bus low state signal LDS and a selection signal RSrj corresponding to the bus low signal BL as shown in FIG. The AND gate 40 outputting the result to the lower lead word line LWrj, the inverted level signal of the bus low state signal LDS output from the inverter 41, and the bus high state corresponding to the bus high signal BH. AND gate 42 for performing logical AND with three inputs of signal HDS and selection signal RSrj, AND gate taking AND for 42 with the input of bus high state signal HDS, buslow state signal LDS and selection signal RSrj-1 of the preceding stage (43) and OR gates 44 for outputting the two AND gates 42 and 43 as two inputs, taking a logical sum, and outputting the result to the upper lead word line HWrj.

When the received data is read in parallel in two bytes, both the bus low state signal LDS and the bus high state signal HDS are high level. At this time, for example, the lead counter 22 indicates the unit memory area REj. When the selection signal RS _rj reaches the selection level, for example, the AND gate 40 of the selector RSEL _j receiving the selection signal RSrj and the next stage are selected. The AND gate 43 of the selector RSEL _{j + 1} outputs a high level signal, and as a result, the reception data of the unit memory area REj is read to the upper lead data lines HDr _{0 to} HDr ₇ as shown in FIG. At the same time, the reception data of the unit memory area REj + 1 is read to the lower lead data lines LDr _{0 to} LDr ₇ .

The received data is read in the upper lead data lines HDr ₀ to HDr ₇ in byte units.

When the received data is read in the lower lead data lines LDr _{0 to} LDr ₇ in byte units, the bus low state signal LDS becomes high level. At this time, for example, when the read counter 22 indicates the unit memory area REj, the AND gate 40 of the selector RSEL _j outputs a high level signal in which all input signals, such as the selection signal RSrj, are high level. As shown in FIG _. 6C, one byte of data is read from the unit memory area REj into the lower read data lines LDr _{0 to} LDr ₇ .

[Receive FIFO memory (6) ... storage data calculation operation]

The calculation unit 15 calculates the accumulated data number of the reception FIFO memory 6 in accordance with the counting operation of the write counter 20 and the read counter 22. The read counter 22 and the write counter 20 repeat counting up according to the read and write operation starting from the reset state of the count values RCOUNTr and RCOUNTw of 0, and n-1 (n denotes that of the receiving FIFO memory 6). After counting up to the number of storage stages, i.e., the unit memory areas RE _{0 to} RE _m , the process returns to zero again. The light counter 20 and the lead counter 22 are not particularly limited but have statuses RSTSw and RSTSr which are inverted each time the count values RCOUNTw and RCOUNTr return to zero. This status RSTSw and RSTSr are reset to 0 in the initial state, and are reversed from 0 to 1 and 1 to 0 whenever the count values RCOUNTw and RCOUNTr return to zero. For example, the light counter 20 and the lead counter 22 are binary counters, and when the storage stage n is equal to 2, the status RSTSw and RSTSr are the next higher digit bits of the most significant bit of the count values RCOUNTr and RCOUNTw. Corresponds to

FIG. 10 shows an example of a transition state of the values of the light counter 20 and the lead counter 22 that change depending on the write and read operations. The state shown in FIG. 10 is a case where the number of storage stages of the reception FIFO memory 6 is four stages. At this time, the write counter 20 and the read counter 22 are each constituted by a 3-bit binary counter. As apparent from FIG. 10, when the status RSTSw and RSTSr coincide with each other, the value obtained by subtracting the count value RCOUNTr of the lead counter 22 from the count value RCOUNTw of the light counter 20 is the accumulated data byte count. When RSTSw and RSTSr do not match, the value obtained by subtracting the count value RCOUNTr of the lead counter 22 from the value obtained by adding the number of storage stages to the count value RCOUNTw of the write counter 20 becomes the accumulated data byte number.

The calculating unit 15 shown in FIG. 1A calculates the number of accumulated data using such a method, so that the comparator 50 for determining the match or inconsistency between the status RSTSw and RSTSr is provided to the comparator 50. When a match is detected by the counter, the count value RCOUNTw of the light counter 20 is output as it is, and when a mismatch is detected, the adder 51 and the output value of the adder 51 add and output the stored number n to the count value RCOUNTW. And a subtractor 52 for subtracting the count value of the lead counter 22 and outputting the accumulated data number. The comparator 50 may be constituted by an exclusive OR gate or an exclusive NOR gate of two input formats. In the former case, a low level is output by matching two inputs, and in the latter case, a high level is output by matching two inputs.

11A and b show an example of the case where the adder 51 is constituted by an integer addition circuit. In the configuration shown in Fig. 11A, the count value RCOUNTw of the light counter 20 is supplied to one input side of the arithmetic logic operator 53, and the storage stage n of the reception FIFO memory 6 is designated to the other input side. Data can be selectively supplied via the multiplexer 54. The multiplexer 54 has a composite gate composed of two AND gates 55, 56 and one OR gate 57 for each bit of the storage unit n-specified data, for example, an exclusive NOR gate. When the output of the comparator 50 is at the low level, the designated data of the storage stage n is output to the arithmetic logic operator 53, and when the level is high, all bits 0 are supplied. In the configuration shown in FIG. 11B, the multiplexer 54 is arranged on the output side of the arithmetic logic operator 53 with respect to the configuration in FIG. 11A, and the coefficient value or the arithmetic logic of the light counter 20 in accordance with the output of the comparator 50. The output value of the calculator 53 is selected.

11C shows an example of an adder 51 configured without using an arithmetic logic operator. In such a configuration, when the number of storage stages of the receiving FIFO memory 6 is equal to 2, the light counter 20 is configured as a binary counter, and the count value RCOUNTw of the light counter 20 is fully decoded to unit memory area. In the case of use in the designation of, the upper digit bit Cu is added after the most significant bit of the count value RCOUNTw output from the light counter 20, and the additional bit Cu is added in accordance with the output of the comparator 50. The multiplexer 58 selects and controls the value at bit 0 or bit 1. In this configuration, giving bit 1 to the additional bit Cu is the same as adding the storage stage to the count value RCOUNTw. Therefore, the structure of the adder 51 can be simplified compared with the case of using an arithmetic logic operator. The multiplexer 58 is composed of two AND gates 59 and 60 and one 0R gate 61, for example, when the output of the comparator 50 composed of an exclusive NOR gate is at a low level. Gives 1 to the additional bit Cu, and 0 for high level. The meaning of the additional bit Cu in the subtractor 52 is different depending on the circuit configuration of the subtractor 52, and can be used as a carry, for example.

[Receive FIFO memory (6) ... transmission ready control]

The transfer preparation generation section 16 is not particularly limited, but is output from the control register 70 and the calculation section 15, in which information for determining assert timing of the DMA transfer request signal DREQ1 can be arbitrarily set by the CPU 9. The outputs of the comparator 71, the empty state detection circuit 29, and the comparator 71 that determine whether the accumulated accumulated data exceeds the set value of the control register 70 are given to the set terminal S and are empty. The output of the detection circuit 29 is provided to the reset terminal R, and a set of outputting the DMA transfer request signal DREQ1 from the output terminal Q, and a reset RS flip-flop 72 are configured. When the accumulated data count of the receiving FIFO memory 6 exceeds the value set in the control register, the RS flip-flop 72 is set by the output of the comparator 71, which causes the DMA transfer request signal DREQ1 to follow. Will be Upon receiving this, the DMA controller 10 accesses the reception FIFO memory 6 via the bus interface unit 5, sequentially reads out and transmits the reception data in the single addressing mode. When the accumulated data count becomes zero due to this data lead, the empty state detection circuit 29 resets the RS flip flop 72 to negate the DMA major request signal DREQ1. When the DMA transfer request signal DREQ1 is negated, the DMAC 10 stops the data transfer control on the data transfer channel. When the number of data transfer words has not reached the required number of words, the DMA transfer request signal is again performed. It waits for DREQ1 to be asserted and intervenes with the rest of the data transfer control. The assert timing of the DMA transfer request signal DREQ1 is determined in accordance with the condition value set in the control register 70. Therefore, by changing the setting value of the control register 70, the number of storage stages of the receiving FIFO memory 6 is changed in appearance, thereby improving the operating efficiency of the system according to the data processing capability or data processing situation of the host system. Adapting or further, the overhead for DMA transfer start can be reduced.

[Transmission FIFO memory (7)]

The transmission FIFO memory 7 is not particularly limited but includes a bit cell array 113 including a plurality of unit memory areas each having 8 bits of bit cells as one unit, and a FIFO control unit for selecting unit memory area selection control and the like. 14) a transfer ready generation unit for generating the DMA transfer request signal DREQ2 by using the calculation unit 115 for calculating the number of data stored in the bit cell array 113 and the accumulated data number acquired by the calculation unit 115 ( 116).

Although not particularly limited, the bit cell array 113 is formed by arranging the bit cells BC in n rows and eight columns as in the receiving FIFO memory 6, and each of the eight bit cells in each row has a unit memory area of 8 bits. _It constitutes _0- TE _m .

The designation of the unit memory area in the data write operation to the bit cell array 113 is executed by the write counter 120, and the write address decoder 121 decodes the coefficient data TCOUNTw to determine the predetermined unit memory area. Is selected. The designation of the unit memory area in the data read operation is performed by the read counter 122, and one unit memory area is selected by the read address decoder 123 decoding the coefficient data TCOUNTr. In the initial state of the transmission FIFO memory 7, the values of the light counter 120 and the read counter 122 are initialized to zero.

[Transmission FIFO memory (7) ... light counter (120)]

The light counter 120 indicates the position of the writeable head unit memory area, and the information is output toward the write address decoder 121. When the write operation of the transmission FIFO memory 7 is specified by the data strobe signal DS, read / write signal R / W, bus low signal BL, and bus high signal BH output from the host device, the bus interface unit 5 reads / writes the data. When the write signal R / W is at the write operation instruction level equal to the low level, the strobe signal TWS is asserted in synchronization with the timing at which the data strobe signal DS is asserted to the high level. In synchronization with this assertion timing, the write address decoder 121 decodes the value of the write counter 120, selects the unit memory area, and writes data to be transmitted to the selected unit memory area. The counter controller 127 increments the light counter 120 in synchronization with the gate timing of the strobe signal TWS, whereby the light counter 120 holds the next write position. Incremental operation of the light counter 120 by the counter controller 127 is determined by the state signals LDS and HDS according to the levels of the bus low signal BL and the bus high signal BH, similarly to the reception FIFO memory 6. That is, when both the bus low signal BL and the bus high signal BH are asserted to the high level and both status signals LDS and HDS are at the high level, that is, both the lower 8 bits and the upper 8 bits of the 16-bit data bus are erased. The counter big controller 127 increments (counts up) the light counter 120 twice using the counter clocks TWC1 and TWC2 while the data transfer is instructed. This is because two unit memory areas are selected at the same time when data is written in units of 16 bits by the host device. When only one of the bus low signal BL and the bus high signal BH is asserted, i.e., the data transfer is instructed to use either the lower 8 bits or the upper 8 bits of the 16-bit data bus. The counter controller 127 increments (counts up) the light counter 120 once using either the count clock TWC1 or TWC2.

Further, in the full state in which data to be transmitted in all unit memory areas TE _{0 to} TE _m is written, that is, the accumulated data number of the bit cell array 113 is equal to the number of unit memory areas, data to be transmitted is no longer transmitted. Can't write. In this state, a full state detection circuit 1260 is provided which determines whether or not the bit cell array 113 is in a full state by receiving the accumulated data number calculated by the calculating unit 115, and detecting the result. The change of the strobe signal TWS is ignored by the signal TES being applied to the write address decoder 121 and the counter controller 127.

[Transmission FIFO memory (7) ... read counter (122)]

The lead counter 122 instructs the position of the lead unit memory area that can be read, and the information is output toward the lead address decoder 123. The transmitting circuit 3 asserts the strobe signal TRS when trying to transmit data. When the strobe signal TRS passes through the gate 125, the read address decoder 123 first decodes the value of the read counter 122 in synchronization with the assert timing of the strobe signal TRS, and the unit selected by the decode result. Data to be transmitted in the storage area is read. Subsequently, the read counter 122 is incremented in synchronization with the gate timing of the strobe signal TRS, whereby the lead counter 122 holds the next read position.

In the empty state in which data is read in all the unit memory areas TE _{0 to} TE _m , new data to be transmitted can no longer be read. In this state, the bit cell array 113 receives the accumulated data number calculated by the operation unit 115 to prevent the read operation of the transmission FIFO memory 7 and further the transmission operation by the transmitter 3. An empty state detection circuit 129 for determining whether the state is empty is provided, and when the detection result signal TES is applied to the gate 125, the strobe signal TRS is the lead counter 122 and the read address decoder. It is not delivered to 123. In addition, a signal substantially identical to the signal TES output from the empty state detection circuit 129 is also given to the transmitting circuit 3, and the operation of the transmitting circuit 3 also depends on the empty state of the transmitting FIFO memory 7. It is supposed to be disabled.

[Transmission FIFO memory (7) ... 2-byte parallel write]

Although each bit cell BC is not particularly limited in order to enable writing of two transmission data in units of one byte (8 bits) in parallel to the bit cell array 113, as shown in FIG. One lead data line Dri (i = 0 to 7) is coupled to the data output terminal Q of the latch circuit 130 via the selection switch 131, and a select switch (1) is respectively connected to the data input terminal D of the latch circuit 130. 132) and 133, the upper right data line HDwi and the lower right data line LDwi are connected in common. The select terminal of the select switch 131 is coupled to the lead word lines Wrj (j = 0 to m), and the select terminals of the select switches 132 and 133 are connected to the upper write word lines HWwj and the lower write word lines LWwj. Each is connected. As shown in FIG. 3, the lead word line Wrj, the upper right word line HWwj, and the lower right word line LWwj are commonly connected to one row and eight bit cells BC constituting one unit storage area, and the lead data line The Dri, the upper right data line HDwi, and the lower right data line LDwi are commonly connected to one column n bit cells BC. The lead data lines Dr _{0 to} Dr ₇ are coupled to the data input terminals of the transmission circuit 3 via the 8-bit internal bus 135 shown in FIG. The lower write data lines LDw ₀ LDw ₇ pass through the 8-bit internal bus 36 shown in FIG. 1b, and the upper write data lines HDw _{0 through} HDw ₇ pass through the 8-bit internal bus 37, respectively. It is connected to the interface unit 5, through which the lower 8 bits and the upper 8 bits of the 16-bit data bus included in the system bus 8 can be interfaced, respectively.

The lead word lines Wr _{0 to} Wr _m are sequentially connected to the output terminals of the lead address decoder 123 which decodes the coefficient value applied by the lead counter 122 to form the selection signals TSr _{0 to} TSr _m . According to the decoding result of the coefficient value imparted at 122, a predetermined one is controlled to a selection level equal to the high level. When one lead word line Wrj is at the selection level, 8-bit transmission data is output from the lead data lines Dr _{0 to} Dr ₇ in the unit memory area TEj consisting of one row and eight bit cells BC connected thereto.

The selection operation of the lower light word lines LWw _{0 to} LWw _m and the upper light word lines HWw _{0 to} HWw _m is executed by the selection control circuit 140 which receives the selection signals TSW _{0 to} TSw _m output from the write address decoder 121. do. The write address decoder 121 sets one of the selection signals TSw _{0 to} TSw _m to a selection level equal to a high level in accordance with the decoding result of the coefficient value provided by the light counter 120.

The selection control circuit 140 controls parallel writing of two bytes of data in one selection operation by the write address decoder 121, and selectors TSEL _{0 to} TSEL provided for each unit memory area TE _{0 to} TE _m . _It is composed of _m .

The selector emitter TSEL ₀ ~TSEL _m includes the same logic gates to each other, for example, the selector TSEL _j is a low state bus selection signal TS and the LDS signal _rn corresponding to the bus low signal BL as shown in FIG. 5 The bus high corresponding to the inversion level signal of the bus low state signal LDS and the bus high signal BH output from the AND gate 140 and the inverter 141 outputting the result of the logical multiplication by taking the logical product and outputting the result to the lower right word line LW _wj . An AND gate 142 for inputting a logical product by inputting the state signal HDS and the selection signal TS _rj three, and an AND gate for inputting the logical product by inputting the bus high state signal HDS and the buslow state signal LDS and the selection signal TSr _il of the preceding stage 3 ( 143, OR gates 144 for inputting two outputs of the two AND gates 142, 143 to perform a logical sum, and outputting the result to the upper lead word line HW _wi .

When the receive data is written in two bytes in parallel, the bus low state signal LDS and the bus high state signal HDS are both at a high level. At this time, for example, the light counter 120 indicates the unit memory area TEj, and when the selection signal TS _rj reaches the selection level, the AND gate 140 and the next stage of the selector TSEL _j receiving this selection signal TS _rj The AND gate 143 of the selector TSEL _{j + 1} outputs a high level signal, and as a result, as shown in FIG. 7A, transmission data of one byte in the upper write data lines HDw _{0 to} HDw ₇ is in the unit memory area. At the same time as TEj is written, another byte of transmission data is written in parallel to the next unit memory area in the lower write data lines LDw _{0 to} LDw ₇ .

When the transmission data is written in the upper write data lines HDw _{0 to} HDw ₇ in byte units, the bus high state signal HDS becomes high level. At this time, for example, when the light counter 120 instructs the unit memory area TEj, the AND gate 142 of the selector TSEL _j , in which all the selected signals, such as the selection signal TS _rj of the selection level, becomes a high level, receives a high level signal. As shown in FIG. 7B, the number of data of one byte is written to the unit memory area TEj via the upper write data lines HDw _{0 to} HDw ₇ .

When the transmission data is written in the lower write data lines LDw _{0 to} LDw ₇ in byte units, the bus low state signal LDS becomes high level. At this time, for example, when the light counter 120 indicates the unit memory area TEj, the AND gate 140 of the selector TSEL _j , in which all input signals such as the selection signal TS _rj of the selection level becomes high level, receives a high level signal. As shown in FIG. 7C, one byte of data is written to the unit memory area TEj via the lower write data lines LDw _{0 to} LDw ₇ .

[Transmission FIFO memory (7) ... storage data calculation operation]

The calculation unit 115 calculates the number of accumulated data in the transmission FIFO memory 7 according to the coefficient movement of the write counter 120 and the read counter 122. The read counter 122 and the write counter 120 repeat counting up according to the read and write operations starting from the reset state of the count values TCOUNTr and TCOUNTw of 0, and n-1 (n denotes the transmission FIFO memory 7). After counting up to the number of storage stages, i.e., the unit memory areas TE _{0 to} TE _m , the process returns to zero again. The light counter 120 and the lead counter 122 are not particularly limited but have statuses TSTSw and TSTSr which invert each time the count values TCOUNTw and TCOUNTr return to zero. This status TSTSw and TSTSr are reset to 0 in the initial state, and are reversed from 0 to 1 and 1 to 0 whenever the count values TCOUNTw and TCOUNTr return to zero. For example, the light counter 120 and the lead counter 122 are composed of binary counters, and when the storage stage n is equal to a power of 2, the status TSTSw and TSTSr are the next higher digits of the most significant bit of the count values TCOUNTr and TCOUNTw. Corresponds to the bit. The transition state of the values of the light counter 120 and the lead counter 122 that changes depending on the write and read operations is basically the same as the state shown in FIG. 10, and the light counter when the status TSTSw and TSTSr coincide with each other. The value obtained by subtracting the count value TCOUNTr of the lead counter 122 from the count value TCOUNTw of 120 is the accumulated data byte number, and when the status TSTSw and TSTSr do not match, they are stored in the count value TCOUNTw of the light counter 120. The value obtained by subtracting the count value TCOUNTr of the lead counter 122 from the value obtained by adding the stage becomes the accumulated data byte number.

The calculating part 115 shown in FIG. 1B calculates the accumulated data number using such a method, and compares the comparator 150 and the comparator 150 to determine the match or inconsistency of the status TSTSw and TSTSr. When a match is detected, the count value TCOUNTw of the light counter 120 is output as it is, and when an inconsistency is detected, the adder 151 and the output value of the adder 151 add and output the stored number n to the count value TCOUNTw. It consists of a subtractor 152 which subtracts the count value of the lead counter 122 and outputs the accumulated data number. In the comparator 150 and the adder 151, the same circuit configuration as that described in the reception FIFO memory 6 can be used.

[Transmission FIFO (7) ... Transmission preparation control]

Although the transfer preparation generation unit 116 is not particularly limited, the control register 170 and the DMA transfer request signal DREQ2 can be arbitrarily set by the CPU 9 to determine the assertion of the DMA transfer request signal DREQ2. The control register 173, in which the information for determining the gate timing can be arbitrarily set by the CPU 9, determines whether or not the number of accumulated data output from the operation unit 115 is less than or equal to the set value of the control register 170. Of the comparator 174 and the comparator 171 for determining whether the accumulated data output from the comparator 171, the empty state detection circuit 129, and the calculation unit 115 is equal to or larger than a set value of the control register 173 or not. An output is provided to the set terminal S and at the same time the output of the comparator 174 is applied to the reset terminal R. The set outputs the DMA transfer request signal DREQ2 at the output terminal Q, and includes a reset type RS flip-flop 172. Stand is constructed. The control register 170 sets a data accumulation number that is an assert condition of the DMA transfer request signal DREQ2, and the other control register 173 sets a data accumulation number that is a negate condition of the signal DREQ2. When the number of accumulated data in the transmission FIFO memory 7 is less than or equal to the value set in the control register 170, the RS flip-flop 172 is set by the output of the comparator 171, whereby the DMA transfer request signal DREQ2. Is asserted. Upon receiving this, the DMA controller 10 writes access to the transmission FIFO memory 7 via the bus interface section 5, and sequentially transfers transmission data from the RAM 11 to the transmission FIFO memory 7 in the single addressing mode.

As a result, when the accumulated data count of the transmission FIFO memory 7 is equal to or higher than the negate condition set in the control register 173, the RS flip-flop 172 is reset by the output of the comparator 174, and the DMA transfer request signal is generated. DREQ2 is negated. When the DMA transfer request signal DREQ2 is negated, the DMAC 10 stops the data transfer control in the data transfer channel and gives up the bus right to the system bus 8 once. In the meantime, the transmitter 3 can sequentially transmit the stored data of the transmission FIFO memory 7 as long as the accumulated data number is not zero. The assert timing and the gate timing of the DMA transfer request signal DREQ2 are determined according to the condition values set in the control registers 170 and 173. Therefore, by changing the setting values of the control registers 170 and 173, the number of storage stages of the transmission FIFO memory 7 is changed in appearance, thereby making the system according to the data processing capability or data processing situation of the host system. Optimizing or further improving the operating efficiency of the system reduces the overhead for DMA transfer start-up.

(Effect obtained by the transmitting FIFO memory 7)

According to the reception FIFO memory 6 and the transmission FIFO memory 7, the following effects are obtained.

The reception FIFO memory 6 and the transmission FIFO memory 7 receive the line control unit 4 and data in units of 8 bits in units of one character, and each of the 8-bit internal buses 36 and 37, respectively. The data can be transmitted to and received from the bus interface unit 5 in units of 16 bits. Therefore, data can be transferred at high speed between the host device such as the CPU 9 and the received data and the data to be transmitted.

One write data line and two read data lines are connected to each bit cell BC of the reception FIFO memory 6, and two write data lines and one read data line are connected to each bit cell BC of the transmission FIFO memory 7. When the 2-byte parallel read through the bus interface unit 5 is performed, the selection control circuit 40 selects the unit memory area indicated by the lead counter 22 of the receiving FIFO memory 6 and the next unit memory area. When the 2-byte parallel writing through the bus interface unit 5 is performed, the selection control circuit 140 selects the unit memory area indicated by the write counter 120 of the transmission FIFO memory 7 and the next unit memory area. Therefore, the FIFO memories 6 and 7 having an 8-bit wide unit memory area can be interfaced with the 16-bit system bus 8 by relatively simple logic.

The selection control circuits 40 and 140 can switch control between 2-byte parallel access and 1-byte access in accordance with the bus low signal BL and the bus high signal BH as bus control signals from the host device. Since the logic is included, it is possible to easily replace the bus replacement by the upper level of the upper CPU 9 without using an external circuit and to improve the convenience of using the FIFO memory.

Computation units 15 and 115 for acquiring the accumulated data number of the reception FIFO memory 6 (transmission FIFO memory 7) include the values of the light counters 20 and 120 and the lead counters 22 and 122. And comparators 50 and 150 that substantially compare the values of), and the values of the light counters 20 and 120 according to the comparison results of the comparators 50 and 150, and the lead counters. The accumulated data number is calculated according to the values of (22) and (122) and the number of storage stages of the unit memory areas RE _{0 to} RE _m and TE _{0 to} RE _m . At this time, the lead counters 22, 122, and the light counters 20, 120 operate separately to give the respective coefficient values to the calculation units 15, 115, and in this way, at both counters, respectively. By the values 15 and 115 being processed by the arithmetic units, the number of accumulated data can be accurately obtained even when reads and writes are generated.

The lead counters 22, 122, and the light counters 20, 120 are provided with the states RSTSr and RSTSw (TSTSr, TSTSw) which are inverted each time the count value is returned to the initial value, and the two states coincide. The number of accumulated data is determined by comparing the values of the lead counters 22 and 122 with the magnitude of the light counters 20 and 120 by determining the inconsistency by the comparators 50 and 150. At the time of operation acquisition, the following large and small discrimination in which the values of the light counters 20 and 120 are returned to their initial values in an order can be easily executed with a simple configuration.

Control registers 70 and 170, which can arbitrarily set the assertion condition of the transmission ready signal such as the DMA transfer request signal DREQ1 (DREQ2) for instructing the data transfer to the host device, furthermore, arbitrarily select the gate condition. The control register 173 that can be set is provided, and the FIFO memory 6 is determined by determining the assertion timing or the gate timing of the transmission ready signal in accordance with the result of the setting of this register and the result of the accumulated data number acquired therein. ), (7) the number of storage stages can be controlled in appearance. Due to this effect, when the load of the host device such as the CPU 9 is low due to the system operation, the accumulated data number of the FIFO memories 6 and 7 is relatively accumulated or the accumulated data number can be increased when the load is large. The flexibility of the system operation can be easily improved. In addition, the above-described effect that the number of storage stages of the FIFO memories 6 and 7 can be controlled in appearance is variable, thereby reducing the frequency of data transfer requests during high-speed operation, i.e., overhead for operating data transfer control. The throughput of the system can be easily improved by reducing the

In particular, in the transmission FIFO memory 7, the negate condition of the transmission ready signal can be controlled variably so that transmission data is sequentially transmitted to several transmission FIFO memories corresponding to each channel of the multi-channel at the time of system rise. If the number of data that is a negate condition during transmission is kept relatively small, the unreasonable aspect of the long bus occupancy period caused by the data transfer to the transmission FIFO memory can be easily solved.

[Acquisition of accumulated data number by using flag]

The accumulated data number of the FIFO memory can be obtained by the configuration of FIG. 12, in addition to the examples of FIGS. 1a and b, which perform addition and subtraction. In Fig. 12, a FIFO memory having four levels of unit memory areas E _{0 to} E ₃ is shown as an example. The light counter 200 sequentially holds a value indicating a unit memory area in which the write is to be executed, and at the decoder 201 as the value of the light counter 200 is decoded by the write address decoder 201. One unit memory area is selected by the selection signals SW _{0 to} SW ₃ to be output, and data is written to it.

Further, the lead counter 202 sequentially holds values indicating the unit memory area to be read, and outputs from the decoder 203 as the value of the lead counter 202 is decoded by the lead address decoder 203. One unit memory area is selected by the selection signals Sr _{0 to} Sr ₃ , and data is read from this unit memory area. Incidentally, the increment operation or the like of the light counter 200 or the lead counter 202 is controlled in the same manner as the description of FIGS. 1A and 1B.

Such a unit storage area in order to obtain the number of accumulated data in the FIFO memory E ₀ ~E ₃ to provide a one-to-one corresponding flag FLG ~FLG ₀ to _3, and each flag FLG ₀ ~FLG ₃ the write address decoder (201 ) Is set to the output signals SW _{0 to} SW ₃ and reset to the output signals Sr _{0 to} Sr ₃ of the read address decoder 203. That is, the flag corresponding to the unit memory area in which data is written is controlled in the set state, and then the flag corresponding to the unit memory area to which data is read is reset. Therefore, the accumulated data number depends on the number of flags in the set state. In Fig. 12, the flags FLG _{0 to} FLG ₃ are constituted by a set and reset RS flip-flop, and the select signals SW _{0 to} SW ₃ are supplied to the set terminal S, and the select signal Sr to the reset terminal R. ₀ ~Sr is ₃ is applied.

In Fig. 12, for example, a logic gate array including an AND 204 and an OR surface 205 is used to obtain the accumulated data number from the outputs of the flags FLG _{0 to} FLG ₃ . The AND surface 204 is formed by arranging data lines X _{0 to} X ₁₂ orthogonal to the output signal lines Y _{0 to} Y ₃ of the flags FLG _{0 to} FLG ₃ and interposing a switch element at a required position indicated by an O table. The selection terminal of each switch element is commonly connected to the output signal lines Y _{0 to} Y ₃ for each column. The switch elements are arranged in an array that can individually determine all combination states when the flags FLG _{0 to} FLG ₃ can be set, and the data line X ₀ provides a signal equal to a high level when the number of accumulated data is four. When the accumulated data number is three, the OR surface 205 is provided, and any one of the data lines X _{1 to} X ₄ gives a signal equal to the high level to the OR surface 205, and the data line X is when the accumulated data number is two. Any one of _{5 to} X ₈ gives a signal equal to the high level to the OR surface 205, and when one accumulated data is one, any one of the data lines X _{9 to} X ₁₂ equals the high level to the OR surface (205). ) The OR surface 205 is formed by arranging three output data lines D _{0 to} D ₂ orthogonal to the data lines X _{0 to} X ₁₂ and interposing a switch element at a required position indicated by an O table. Each switching element is described as 3-bit data to be stored data to the output data line D ₀ ~D ₂ according to the state of the selection terminal is connected to the data lines X ₀ ~X ₁₂ for each row, the data line X ₀ ~X ₁₂ It is supposed to output. In this way, the number of accumulated data given to the output data lines D _{0 to} D ₂ is used for the transfer preparation control and the like. As described above, even when the accumulated data number is acquired using the flags FLG _{0 to} FLG ₃ , the output coefficient values of the lead counter 202 and the light counter 200 which are operated separately are used as the reference. You can get the date correctly.

[External output of accumulated data number]

The accumulated data count of the FIFO memory is not only used for the transmission preparation control but may be output directly to the outside. For example, according to the configuration of FIGS. 1A and 1B, a register is provided to hold the accumulated data numbers acquired by the calculation units 15 and 115, respectively, and the registers are transferred to the CPU 9 via the bus interface unit 5. The host device such as the above becomes directly accessible. As a result, the CPU 9 can know the accumulated data number of the reception FIFO memory 6 and the transmission FIFO memory 7 at a necessary timing.

For example, when performing data transmission / reception in HDLC (High-level Data Link Control) order, the number of accumulated data is monitored or a frame check sequence is used to quickly read and process control field control information from the receiving FIFO memory 6. When information is received, it is determined by how many bytes of data in the information field remain in the reception FIFO memory 6, or determined in accordance with the reception information so that the upper CPU 9 can efficiently process the protocol and execute detailed control. It becomes possible.

13 shows a FIFO memory, which is another embodiment of the present invention. The FIFO memory 301 shown in FIG. 13 is not particularly limited but includes one functional module included in the microcomputer or processor 302 shown in FIG. The processor 302 is not particularly limited, but is formed on one semiconductor substrate such as a silicon substrate by a known technique for manufacturing a semiconductor integrated circuit.

First, the processor 302 will be described schematically.

In FIG. 14, the CPU 303 and the serial input circuit 304 are representatively shown in addition to the FIFO memory 301. The serial input circuit 304 synchronizes or recovers the received data RxD supplied to the serial bits, and converts the input data in parallel to output them.

The FIFO memory 301 is used as a buffer memory for storing data supplied from the serial input circuit 304. This FIFO memory 301 is interfaced separately from the serial input circuit 304 side and the central processing unit 303 side.

The interface data on the side of the serial input circuit 304 is supplied with the reception data Drx converted in parallel on the side of the serial input circuit 304 and the push signal PUSH for instructing the write of the reception data Drx to the FIFO memory 301. . The full input signal FS for notifying the FIFO memory 301 that there is no free memory is supplied to the serial input circuit 304 from the interface unit on the serial input circuit 304 side of the FIFO memory 301.

The interface unit on the side of the central processing unit 303 receives the data Di or the address signal Ai from the central processing unit 303 via the address bus ABUS and the data bus DBUS, and at the same time receives a predetermined bit of the address Ai. The decoder 305 receives the control signals AA and CA generated by decoding, and receives the read / write signals R / W. The half signal ES and the FIFO by the central processing unit 303 to inform the central processing unit 303 of the interface unit on the central processing unit 303 side that there is no data to be read to the FIFO memory 301. The access inhibited state signal INH is provided to instruct the memory 301 to prohibit the access operation.

Although the central processing unit 303 is not particularly limited, the central processing unit 303 is in charge of controlling the entire processor and also performs protocol processing for the received data RxD.

Next, the FIFO memory 301 will be described in detail with reference to FIG. The FIFO memory 301 basically performs input / output of data in a first-in first-out format, but furthermore, the central processing unit 303 is configured to enable random access and unnecessary data clear processing.

In Fig. 13, reference numeral 310 denotes a memory cell array in which a plurality of rewritable memory cells, for example, static memory cells, are arranged in a matrix. The select terminals of the memory cells included in the memory cell array 310 are coupled to word lines WL _{0 to} WL _n for each column, and the data input / output terminals of the memory cells are complementary bit lines BL ₀ , BL _{0 to} BL _n , for each row. It is coupled to a complementary bit line BL _n thereof _{BL 0, BL 0 ~BL n,} BL n is through the row selection circuit 306 is connected to a complementary common data line (307). Addressing of necessary memory cells included in the memory cell array 310 is performed by the word line selection decoder 311 and the bit line selection decoder 312.

That is, the word line selection decoder 311 reads the address signal supplied thereto to drive the predetermined word line at the selection level. The bit line select decoder 312 controls the row select circuit 306 to decode the address signal supplied thereto and to conduct a predetermined complementary bit line to the complementary common data line 307. The read circuit of the data to the memory cells addressed by these word line select decoders 311 and bit line select decoders 312 is not particularly limited, but a read circuit 308 including a sense amplifier 308A and an output gate 308B. Write of data to the addressed memory cell is not particularly limited but is performed by the write circuit 309 including two input gates 309A, 309B and the write amplifier 309C.

The address signal Ai for random access by the central processing unit 303 is supplied to the address input buffer 315. The FIFO memory 301 also provides a lead address counter 313 and a write address counter 314 composed of a binary counter or the like for generating an access address therein. The write address 314 sequentially outputs the write address Aw for each data write operation by the first-in type. Incremental operation of the write address counter 314 is instructed by the control signal? Wi output from the controller 317 being asserted. The read address counter 313 sequentially outputs the read address Ar for each data read operation by the selection format. Incremental operation of this lead addresser 313 is instructed by the control signal? Ri output from the controller 317 being asserted.

The selector 316 selects the address signal Ai inputted internally by the address input buffer 315, the address signal Ar output from the lead addresser 313, and the address signal Aw outputted from the write addresser 314. And is supplied to the word line selection decoder 311 and the bit line selection decoder 312. The selection control of the selector 316 is executed in accordance with the control signal .phi. Of the plurality of bits output from the controller 317.

The values of the lead addresser 313 and the write addresser 314 are coincident in the initial state, and the address signal Ar output from the lead addresser 313 and the address signal Aw output from the write addresser 314. Is supplied to the comparison determination circuit 318 so that the coincidence and inconsistency are always monitored. The comparison decision circuit 318 sets the full signal FS to a high level to inform the serial input circuit 304 that a new write cannot be executed when it detects that both values Ar and Aw coincide in the write operation of the first-in-one type. If it asserts and detects that the values Ar and Aw coincide in the read operation of the elected form, the empty signal ES is set to a high level to inform the central processing unit 303 that the data to be read is no longer present. I do it. The comparison determination circuit 318 is not particularly limited, but the first input type detects the write operation in accordance with the incremental instruction of the write address counter 314 by the control signal .phi.wi, and the lead address counter (by the control signal .phi.ri). According to the increment instruction of 313, a lead operation of the elected type is detected.

The output terminal of the output gate 308A included in the lead circuit 308 and the input terminal of the input gate 309A included in the write circuit 309 are connected to the memory lead of the electoral type by the central processing unit 303. The input terminal of the input gate 309B, which is interfaced to the data DBUS via the data input / output buffer 320 used for random access, and is included in the write circuit 309, is a memory write of the first-in type by the serial input circuit 304. It is interfaced to the serial input circuit 304 via a data input buffer 321 used for access. The input / output control of data to the data input / output buffer 320 is executed by the control signals phi i and phi o output from the controller 317 in accordance with the level of the read / write signal R / W. The input control of data by the data input buffer 321 is executed by the control signal .phi.p output from the controller 317. Although not particularly limited, the read / write control of the read circuit 308 and the write circuit 309 in the elected type memory lead access and the random access by the central processing unit 303 is performed by the read / write signal R / W. The control signals? R and? W outputted from the controller 317 are output according to the level, and the write control of the write circuit 309 is controlled to the control signal .phi. Is indicated by The operation instruction to the write amplifier 309C is not particularly limited, but is given by the output signal of the OR gate 309D which takes a logical sum of the control signals phi p and phi w.

The lead addresser 313 and the write addresser 314 have a preset function, are coupled to the data input / output buffer 320 via an internal data bus 325, and the address signals Ar and Aw held by the central processing unit. 303 reads or rewrites the value. The input / output gate of the read address counter 313 coupled to the data input / output buffer 320 is opened and closed by the control signal Φ rac output from the controller 317. Similarly, the input / output gate of the write address counter 314 coupled to the data input / output buffer 320 is opened and closed by the control signal .phi.wac output from the controller 317.

Here, the control signal AA output from the decoder 305 is regarded as a signal instructing to randomly access the FIFO memory 301 by the address signal Ai by its high level. When the control signal AA is asserted to the high level, the controller 317 selectively outputs the address signal Ai to the selector 316 by the control signal .phi.s. The read and write operations in this random access are instructed by the read / write signals R / W. When the memory lead operation is instructed by this, the control signals? R and? O are asserted, and the control signals? W and? I are gated. When the memory write operation is instructed, the control signals .phi.r and .phi.o are gated, and the control signals .phi.w and .phi.i are asserted.

The two-bit control signal CA output from the decoder 305 becomes a control signal for instructing the access of the read addresser 313 or the write addresser 314. The predetermined one bit included in the control signal CA is regarded as a bit for instructing access to the lead addresser 313 by its high level, and the other one bit is accessed to the write addresser 314 by its high level. Is considered a bit indicating. When access to the lead address counter 313 is instructed by the control signal CA, the controller 317 asserts the control signal? Rac to open an input / output gate (not shown) of the lead address counter 313. When the control signal CA instructs access to the write address counter 314, the controller 317 asserts the control signal? Wac to open an input / output gate (not shown) of the write address counter 314. At this time, the read / write operation is instructed by the read / write signal R / W, and either of the control signals phi i and phi o is asserted accordingly, and thus the input / output direction of the data in the data input / output buffer 320 is changed. Controlled. When the lead address counter 313 and the write address counter 314 are accessed, both the control signals .phi.r and .phi.w are negated.

When the read operation is instructed by the read / write signal R / W when the control signal AA is gated to the low level, the FIFO memory 301 reads in the selection form according to the output address signal Ar of the read address counter 313. The operation mode is entered. As a result, the control signal .phi.ri is asserted so that the lead address counter 313 is incremented, and the address signal Ar output from the incremented lead address counter 313 is selected via the selector 316 to select a word line. The decoder 311 and the bit line selection decoder 312 are supplied.

The push signal PUSH supplied from the serial input circuit 304 is regarded as a signal indicative of the write operation mode by the first-in-one format according to the output address signal Aw of the write address counter 314 by its high level.

The controller 317 asserts the control signal? Wi when the push signal PUSH is asserted to the high level, thereby incrementing the write address counter 314, and thus the address Aw thus obtained is selected by the selector 316. The word line selection decoder 311 and the bit line selection decoder 312 are supplied via the above.

The FIFO memory 301 of this embodiment is accessible from both the central processing unit 303 and the serial input circuit 304, so that the controller 317 is centrally processed, although not particularly limited to avoid contention of access from both sides. In order to prohibit access of the FIFO memory 301 by the device 303, an access prohibition status signal INH is given.

Although the logic of avoiding contention is not particularly limited, the access request from the serial input circuit 304 is prioritized, and the access inhibited state signal INH is asserted in accordance with the assert period of the push signal PUSH, for example.

Next, the operation of the FIFO memory 301 will be described.

The serial input circuit 304 asserts the push signal PUSH on the condition that the full signal FS is gated, and supplies the reception data Drx to the FIFO memory 301. As a result, the FIFO memory 301 incrementally stores the received data Drx in the memory cell array 310 while incrementing the write address counter 314.

The central processing unit 303 instructs the FIFO memory 301 in a read operation according to the elected form, provided that the empty signal ES and the access inhibited state signal INH are gated. As a result, the FIFO memory 301 sequentially reads the reception data stored in the memory cell array 310 while incrementing the read address counter 313.

Here, an operation of clearing this when unnecessary data occurs in the middle of the reception data stored in the memory cell array 310 due to an error in system operation or the like will be described. For example, as shown in FIG. 15A, the regions ED1 and ED2 in the address space of the memory cell array 310 when the read address counter 313 and the write address counter 314 indicate certain values Ar and Aw. In the case where the data is no longer needed, the central processing unit 303 rewrites the value of the lead addressing counter 313 to Ar 'as shown in FIG. 15B, and sets the value of the light addressing counter 314 to Aw. Rewrite to '. In this way, when the values of the lead addresser 313 and the write addresser 314 are rewritten, the reception data Drx applied from the serial input circuit 304 thereafter is the address of the value Aw 'indicated by the write addresser 314. Unnecessary data remaining in the area ED2, which is sequentially written from, is ignored. After that, when the central processing unit 303 reads the reception data stored in the memory cell array 310 in the elected format, the area is sequentially read from the address Ar 'indicated by the read address counter 313. Data remaining in ED1 is ignored. Therefore, the central processing unit 303 rewrites the values of the lead addresser 313 and the write addresser 314 without sequentially reading all unnecessary data and updating the value of the lead addresser 313. By simply executing, the actual clear processing for unnecessary data can be performed easily.

In this clearing process, the central processing unit 303 needs to know the states of the address counters 313 and 314 when the read address counter 313 and the write address counter 314 are rewritten. In this case, the central processing unit 303 reads the values of the lead addresser 313 and the write addresser 314 to calculate the values Ar 'and Aw' to be rewritten according to the read values Ar and Aw.

Such a read access of the address counters 313 and 314 is required, for example, when the CPU 303 recognizes only the package number, byte number, or word count of unnecessary data. It is assumed that the values Ar and Aw, which should be the basis of the physical address space of the parentheses) or the values Ar 'and Aw' to be calculated, must be obtained.

Next, when the system operation requires the inspection of data stored in the middle of the FIFO memory 301, the central processing unit 303 randomly accesses the FIFO memory 301 by the address signal Ai and reads out necessary data. In this read operation, the control signal .phi ri is not asserted, whereby the value of the lead address counter 313 is maintained as it is. When the central processing unit 303 needs the address of the physical address space of the FIFO memory 301 or the necessary address to be accessed at this random access, the central processing unit 303 reads. The address counter 313 and the write address counter 314 can be read accessed to read the value.

According to the FIFO memory 301, the following effects are obtained.

By selecting the external address signal Ai from the selector 316, the central processing unit 303 keeps the addresses indicated by the lead addresser 313 and the write addresser 314 as they are. The necessary data can be obtained at the address of [0100]. This enables random access even if the order of reading and writing data is specified by the values of the built-in address counters 313 and 314.

When unnecessary data occurs in the middle of the data stored in the memory cell array 310, the value of the read address counter 313 or the write address counter 314 is rewritten under the control of the central processing unit 303, and thus the FIFO memory ( Substantial clear processing of the data in 301 can be performed easily.

By the above effect, when the FIFO memory 301 capable of random access by the central processing unit 303 and arbitrary clear processing of unnecessary data is used as the buffer memory of the serial input circuit 304, the central processing unit 303 When the protocol processing for the received data is to be executed, the central processing unit 303 randomly accesses the FIFO memory 301 to arbitrarily obtain information such as control fields included in the received data and execute the protocol processing. Unnecessary data such as unnecessary reception data or transmission source identification data included in the reception data can be easily cleared on the FIFO memory 301 serving as a buffer memory. Therefore, it is not necessary to execute the protocol process after all the data stored in the FIFO memory 301 is transferred to the local memory or the like, whereby the protocol process can be made more efficient and the system can be simplified. .

[FIFO Memory (331)]

16 shows another FIFO memory 331 according to the present invention. The FIFO memory 331 shown in FIG. 16 is not particularly limited, but is composed of one peripheral device included in the microcomputer system shown in FIG. 17, and is formed by a known semiconductor integrated circuit manufacturing technology. It is formed on two semiconductor substrates.

In FIG. 17, a processor 333 as a bus master module other than the FIFO memory 331, a serial input circuit 334, and a bus arbiter 332 for performing bus winding adjustment are representatively shown. It is coupled to DBUS, address bus ABUS and control bus CBUS. The processor 333 and the serial input circuit 334 output bus request signals BREQ1 and BREQ2 as signals for requesting a bus ticket, and the bus arbiter 332 which receives these bus request signals BREQ1 and BREQ2 is the processor 333 or the serial. One of the input circuits 334 outputs bus confirmation signals BACK1 and BACK2 for recognizing the bus ticket.

The serial input circuit 334 synchronizes or recovers the received data RxD supplied to the serial bits, and outputs the fetched data in parallel. The FIFO memory 331 is used as a buffer memory for storing data supplied from the serial input circuit 334. The processor 333 is not particularly limited, but is also configured to execute data processing such as protocol processing for received data stored in the FIFO memory 331. The FIFO memory 331 is constituted by a single chip or a single pellet, and provides a single interface unit for general use. This interface unit is coupled to the data bus DBUS, address bus ABUS and control bus CBUS. The FIFO memory 331 receives a read / write signal R / W output from the processor 333 or the serial input circuit 334 via the control bus CBUS, and at the same time, the FIFO memory 331 has no empty memory cells. In particular, an empty signal for outputting the full signal FS for notifying the serial input circuit 334 to the control bus CBUS and for notifying the external, in particular, the processor 333 of a state in which there is no data to be read in the FIFO memory 331. Output ES to control bus CBUS. The FIFO memory 331 receives the control signals AA and CA generated by decoding the predetermined bit of the address signal Ai output from the processor 333 or the serial input circuit 334 by the decoder 335.

Next, the FIFO memory 331 will be described in detail with reference to FIG. The FIFO memory 331 basically executes input and output of data in a first-in first-out format, but furthermore, the processor 333 is configured to enable random access and unnecessary data clear processing. In FIG. 16, reference numeral 340 denotes a memory cell array in which a plurality of rewritable memory cells, for example, static memory cells, are arranged in a matrix. The select terminals of the memory cells included in the memory cell array 340 are coupled to word lines WL _{0 to} WL _n for each column, and the data input and output terminals of the memory cells are complementary bit lines BL ₀ and BL _{0 to} BL _n for each row. , is coupled to BL _n, these complementary bit lines _{BL 0, BL 0 ~BL n,} BL n is through the row selection circuit 350 is connected to a complementary common data line (351). The address selection of the necessary memory cells included in the memory cell array 340 is performed by the word select decoder 352 and the bit line selection decoder 353. That is, the word line selection decoder 352 decodes the address signals supplied thereto and drives the predetermined word line to the selection level.

The bit line selection decoder 353 controls the row selection circuit 350 to decode the address signals supplied thereto and to conduct the predetermined complementary bit line to the complementary common data line 351. The read of the data to the memory cells addressed by these word line select decoders 352 and bit line select decoders 353 is not particularly limited, but the read circuit 354 including the sense amplifier 354A and the output gate 354B. The writing of data to the addressed memory cells is performed by the write circuit 355 including the input gate 355A and the write amplifier 355B, although not particularly limited.

The address signal Ai for random access by the processor 333 is supplied to the address input buffer 345. In addition, the FIFO memory 331 provides a lead address counter 343 and a write address counter 344 composed of a binary counter or the like for generating the access address therein. The write address 344 incrementally outputs the write address Aw for each data write operation by the first-in, first-out format. Incremental operation of the write address counter 344 is instructed by the control signal? Wi output from the controller 347 being asserted. The lead address counter 343 increments and outputs the lead address Ar in sequence for each data read operation by the first-in, first-out form. Incremental operation by the lead addresser 343 is instructed by the assertion of the control signal? Ri output from the controller 347.

The selector 346 selects an address signal Ai fetched from the address input buffer 345, an address signal Ar output from the lead addresser 343, and an address signal Aw output from the write addresser 344. The word line selection decoder 354 and the bit line selection decoder 354 are then supplied. The selection control of the selector 346 is executed in accordance with the multi-bit control signal .phi. Output from the controller 347.

The values of the lead addresser 343 and the write addresser 344 coincide with each other in an initial state, and the address signal Ar output from the lead addresser 343 and the address signal Aw output from the write addresser 344. Is supplied to the comparison determination circuit 348 so that its match or discrepancy is always monitored. The comparison decision circuit 348 sets the full signal FS to a high level to inform the serial input circuit 334 of a state in which a new light cannot be received when it detects that the values Ar and Aw coincide with each other in the write operation of the first type. When asserting and detecting that the values Ar and Aw coincide in the read operation of the elected form, the empty signal ES for informing the processor 333 that the data to be read no longer exists is asserted to a high level. . The comparison determination circuit 348 is not particularly limited but detects the write operation of the first-input type according to the incremental instruction of the write address counter 344 by the control signal .phi. According to the increment instruction of 343, the lead operation of the elected type is detected.

The output terminal of the output gate 354B included in the read circuit 354 and the input terminal of the input gate 355A included in the write circuit 355 are interfaced to the data bus DBUS via the data input / output buffer 350. The input / output control of the data to the data input / output buffer 350 is executed by the control signals phi i and phi o output from the controller 347 in accordance with the level of the read / write signal R / W. The read / write control of the read circuit 354 and the write circuit 355 is instructed by the control signals? R and? W output from the controller 347 according to the level of the read / write signal R / W.

The lead addresser 343 and the write addresser 344 have a preset function and are coupled to the data input / output buffer 350 via an internal data bus 360, and maintain the address signals Ar and Aw held by the processor 333. Is read or the processor 333 can rewrite the value. The lead address counter 343 coupled to the data input / output buffer 350 is opened and closed by the control signal Φ rac output from the control 347.

Similarly, the input / output gate of the write address counter 344 coupled to the data input / output buffer 350 is opened and closed by the control signal .phi.wac output from the control 347.

Here, the control signal AA output from the decoder 355 is regarded as a signal instructing random access to the FIFO memory 331 by the address signal Ai by its high level. The controller 347 selects and outputs the address signal Ai to the selector 346 when the control signal AA is asserted to the high level.

The read / write operation in this random access is instructed by the read / write signal R / W output from the processor 333. When the memory lead operation is instructed by this, the control signals? R and? O are asserted, the control signals? W and? I are gated, and the control signals? W and? I are asserted.

The 2-bit control signal CA output from the decoder 335 becomes a control signal for instructing the access of the read addresser 343 or the write addresser 344. The predetermined one bit included in the control signal CA is regarded as a bit for instructing access to the lead addresser 343 by its high level, and the other one bit is accessed to the write addresser 344 by its high level. Is considered a bit indicating. When the control signal CA is instructed to access the lead address counter 343, the controller 347 asserts the control signal? Rac to open an input / output gate (not shown) of the lead address counter 343. When the control signal CA is instructed to access the write address counter 344, the controller 347 asserts the control signal? Wac to open an input / output gate (not shown) of the write address counter 344. At this time, the read / write operation is instructed by the read / write signal R / W. As a result, one of the control signals phi i and phi o is asserted to change the input / output direction of the data in the data input / output buffer 350. Controlled. When the lead address counter 343 or the write address counter 344 is accessed, both the control signals .phi.r and .phi.w are negated.

When the control signal AA is gated to the low level, if the read operation is instructed by the read / write signal R / W, the FIFO memory 331 is in accordance with the selection form according to the output address signal Ar of the read address counter 343. The lead operation mode is entered. As a result, the control signal .phi.ri is asserted so that the lead address counter 343 is incremented, and the address signal Ar output from the incremented lead address counter 343 is selected via the selector 346 to select a word line. The decoder 352 and the bit preselection decoder 353 are supplied.

When the write operation is instructed by the read / write signal R / W when the control signal AA is gated to the low level, the FIFO memory 331 writes the data according to the first-in-one format according to the output address signal Aw of the write addresser 344. The operation mode is entered. When the control signal? Wi is asserted, the write address counter 344 is incremented, and the address signal Aw outputted from the incremented write address counter 344 is selected via the selector 346 to select a word line. The decoder 352 and the bit preselection decoder 353 are supplied.

The FIFO memory 331 of this embodiment can be accessed via a common interface from both the processor 333 and the serial input circuit 334, but the bus winding of the processor 333 and the serial input circuit 334 is a bus arbiter ( Since it is recognized by either side 332, access contention on both the processor 333 and the serial input circuit 334 with respect to the FIFO memory 331 is prevented by the bus winding adjustment by the bus arbiter 332. .

Next, the operation of the FIFO memory 331 will be described.

The serial input circuit 334 asserts the bus request signal BREQ2 when the full signal FS is not asserted, and outputs an address signal Ai capable of making the control signal AA low level when the bus ticket is acknowledged for this request. At the same time, the read / write signal R / W is set at the low level to instruct the FIFO memory 331 to write in the form of a first-in, first-out, and then the reception data Drx is output to the data bus DBUS. In response to this, the FIFO memory 331 increments the write address counter 344 and sequentially stores the received data Drx in the memory cell array 340.

The processor 333 asserts the bus request signal BREQ1 when the empty signal ES is not asserted, and outputs an address signal Ai capable of bringing the control signal AA low when the bus ticket is recognized for this request. At the same time, the read / write signal R / W is set to the high level to instruct the FIFO memory 331 in a read operation according to the elective format. As a result, the FIFO memory 331 sequentially reads the reception data stored in the memory cell array 340 while incrementing the read address counter 343.

In this case, when unnecessary data occurs in the middle of the reception data stored in the memory cell array 340 due to an error in the system operation, the operation for clearing this is similar to the case of the FIFO memory 301, for example, in FIG. 15A. As shown in the figure, when the read address counter 343 and the write address counter 344 indicate certain values Ar and Aw, data of the areas ED1 and ED2 in the address space of the memory cell array 340 becomes unnecessary. As shown in FIG. 15B, the processor 333 rewrites the value of the lead address counter 343 to Ar 'and rewrites the value of the write address counter 344 to Aw'. In this manner, when the values of the lead addresser 343 and the write addresser 344 are rewritten, the reception data Drx given by the serial input circuit 334 is then set to the value Aw 'indicated by the write addresser 344. Unnecessary data that is sequentially written at the address and remaining in the area ED2 is ignored. Subsequently, when the processor 333 reads the reception data stored in the memory cell array 340 in the elected format, it is sequentially read at the address Ar 'indicated by the read address counter 343, and is stored in the area ED1. Remaining data is ignored.

Therefore, the processor 333 simply rewrites the values of the lead addresser 343 and the write addresser 344 without having to read all unnecessary data sequentially and update the value of the lead addresser 343. Substantial clear processing can be performed simply.

In this clearing process, when the processor 333 needs to know the states of the address counters 343 and 344 when the read address counter 343 and the write address counter 344 are rewritten, The processor 333 reads the values of the read addresser 343 and the write addresser 344, and calculates values Ar 'and Aw' to be rewritten according to the read values Ar and Aw.

Next, when it is necessary to inspect data stored in the middle of the FIFO memory 331 due to system operation, the processor 333 randomly accesses the FIFO memory 331 by the address signal Ai and reads out necessary data. In the read operation at this time, the control signal .phi ri is not asserted, whereby the value of the lead address counter 343 is maintained as it is. If the processor 333 needs address information as a reference for the physical address space of the FIFO memory 331 or a necessary address to be accessed during this random access, the processor 333 read-out counter 343. ) And the write address counter 344 can be read to read the value.

Similarly to the FIFO memory 301, the FIFO memory 331 also allows random access while the data read / write order is defined by the values of the built-in addressers 343 and 344. Clear processing can be easily performed. When the processor 333 intends to execute the protocol processing for the received data by these, it is not necessary to execute the protocol processing after transferring all the data stored in the FIFO memory 331 to the local memory. Can be planned.

As mentioned above, although the invention made by the present inventor was demonstrated concretely according to the Example, this invention is not limited to the said Example and can be variously changed in the range which does not deviate from the summary.

For example, a host device such as the CPU 9 may be incorporated in the communication control device 1 composed of one LSI. In addition, the reception circuit 2 and the transmission circuit 3 can be multichannel, and in this case, a FIFO memory can be provided for each communication channel. In addition, the bit width of the unit memory area is not limited to 8 bits. In addition, the relationship between the number of parallel lead bits and the number of parallel write bits in the FIFO memories 6 and 7 is not limited to a double relationship as in the above embodiment, but a relationship of an integer multiple of 2 times or more to 4 times and the like. Can be changed to

Although the functional modules for accessing the FIFO memories 301 and 331 have been described as a central processing unit, a processor, and a serial input circuit, the present invention is not limited thereto, and a direct memory access controller, a parallel input circuit, or the like may be included. good. The control signals for determining the operation modes of the FIFO memories 301 and 331 are not limited to the control signals AA and CA described in the above embodiments, and may be appropriately changed, and the generation method thereof may be variously changed. Also, the clear processing in the FIFO memories 301 and 331 is not limited to the contents described with reference to Figs. 15a and b. For example, when there is unnecessary data only in the area ED1 of Fig. 15a, Just rewrite the value. Similarly, when there is unnecessary data only in the area ED2 of FIG. 15A, only the value of the write address counter needs to be rewritten.

In the above description, the invention made mainly by the present inventors has been described in the case where the invention is applied to the communication control device or the reception memory buffer memory, which is the background of the application, but the present invention is not limited thereto, but the floppy disk controller or the hard disk controller is not limited thereto. Furthermore, it can be widely applied to FIFO memory itself composed of one LSI.

Claims (20)

An input circuit for fetching data, a buffer memory for accumulating the data supplied from the input circuit, and a processor for controlling the input circuit and the buffer memory to execute predetermined protocol processing for the data accumulated in the buffer memory And a bus coupled to the input circuit, the buffer memory, and the processor, the bus configured to transfer the data, the buffer memory comprising: a memory cell array having a plurality of memory cells for accumulating the data; A read address counter for generating a read address for reading the data in a memory cell for each read operation; a write address counter for generating a write address for writing the data supplied from the input circuit to the memory cell for each write operation; A selection decoder circuit for selecting the plurality of memory cells in the memory cell array by supplying a read address or a write address, a read circuit for reading the data accumulated in the memory cell selected in accordance with the read address, the read circuit A write circuit for writing the data input from the input circuit via the bus to the memory cell selected in accordance with the write address, the data coupled to the bus and supplied from the bus to the write circuit A data input / output buffer for outputting the data supplied from the bus, the read address counter, the write address counter, the write circuit, the internal bus coupled to the read circuit and the data input / output buffer, and the output from the processor. The first control signal generated according to the dress signal is supplied so that the counter value supplied to the lead addresser or the write addresser from the processor through the bus, the data input / output buffer and the internal bus can be written. And a controller configured to generate and output a second control signal. 2. The controller of claim 1, wherein the controller supplies a counter value in the read address counter or the write address counter by supplying a third control signal generated according to an address signal output from the processor. And generating and outputting a fourth control signal to be readable to said processor via said bus. 3. The microcomputer system according to claim 2, wherein said lead addresser increments said lead address every time a read operation. 4. The microcomputer system according to claim 3, wherein said write addresser increments said write address every time a write operation is performed. 5. The microcomputer system according to claim 4, wherein said buffer memory is a first in first out memory for accumulating said data in a first-in first-out format. 6. The buffer memory according to claim 5, wherein the buffer memory has a decision circuit for determining whether the read address and the write address match or do not coincide, and the decision circuit includes the read address and the read address during the write operation of the buffer memory. When a match of the write addresses is detected, a fifth control signal is outputted to the input circuit indicating that the data to be written to the buffer memory can no longer be fetched, and the determination circuit is configured to perform the read operation of the buffer memory. And a sixth control signal to the processor, when a match between the read address and the write address is detected, indicating that there is no data to be read in the buffer memory. 7. The microcomputer system according to claim 6, wherein said input circuit converts said data supplied as serial bits in a communication line in parallel and outputs them to said bus. 8. The microcomputer system of claim 7, wherein the bus includes a data bus for transmitting the data, an address bus for transmitting an address signal output from the processor, and a control bus for transmitting the plurality of control signals. The microcomputer system of claim 8, further comprising a decoder configured to generate the first control signal according to an address signal output from the processor. 6. The microcomputer system according to claim 5, wherein said plurality of memory cells are static memory cells. 6. The buffer memory of claim 5, wherein the buffer memory outputs an address input buffer for fetching the address signal supplied from the processor via the bus, the address signal output from the address input buffer, the read address counter and the write address counter. And a selector for selectively selecting the read addresses and the write addresses to be supplied to the selection decoder circuit, and wherein the controller is configured to receive an eighth control signal in response to a seventh control signal generated according to the address signal output from the processor. A control signal, wherein said selector selects said address signal output from said processor in response to said eighth control signal; 12. The microcomputer system according to claim 11, wherein said input circuit converts said data supplied as serial bits in a communication line in parallel and outputs them to said bus. 13. The microcomputer system of claim 12, wherein the bus comprises a data bus for transmitting data, an address bus for transmitting the address signal, and a control bus for transmitting the plurality of control signals. 14. The microcomputer system according to claim 13, comprising a decoder for generating said seventh control signal in accordance with said address signal. 15. The microcomputer system according to claim 14, wherein counter values of the read address counter and the write address counter coincide in the state where the data does not exist in the memory cell. 15. The microcomputer system according to claim 14, wherein the data input / output buffer controls the transmission direction of the data by ninth and tenth control signals generated according to a read / write signal supplied from the processor via the bus. 17. The microcomputer system according to claim 16, wherein the comparison determination circuit detects a read operation and a write operation of the buffer memory based on the second and fourth control signals. 16. The microcomputer system according to claim 15, wherein the microcomputer system having the input circuit, the buffer memory, the bus and the processor is formed on one semiconductor substrate. 12. The microcomputer system according to claim 11, wherein the microcomputer system having the input circuit, the buffer memory, the bus and the processor is formed on one semiconductor substrate. A buffer memory for accumulating data, a processor for controlling the buffer memory to execute predetermined protocol processing on the data accumulated in the buffer memory, a bus coupled to the buffer memory and the processor, and transferring the data; A microcomputer system configured, wherein the buffer memory includes: a memory cell array having a plurality of memory cells for accumulating the data; a read address counter for generating a read address for reading the data from the memory cell at every read operation; The write address counter which generates a write address for writing data to the memory cell for each write operation, the address signal output from the processor, the read address or the write address is supplied to the memory cell array. A selection decoder circuit for selecting the plurality of memory cells, a read circuit for reading the data stored in the memory cell selected according to the address signal output from the processor, selected according to the address signal output from the processor And a write circuit for writing the data input from the processor to the memory cell via the bus. A data input / output buffer coupled to the bus and supplying the data input from the bus to the write circuit and outputting the data supplied from the read circuit to the bus, the write circuit, the read circuit and the data input / output buffer. An internal bus coupled, an address input buffer for fetching the address signal supplied from the processor via the bus, the address signal output from the address input buffer and the read address output from the read address counter and the write address counter; And a controller for selectively selecting a write address and supplying the selected address to the selection decoder circuit and generating a second control signal in response to the first control signal generated according to the address signal output from the processor. Above And selecting the address signal output from the processor in response to a second control signal.