JP2740031B2 - Data receiving device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to a data receiving apparatus of a local area network (hereinafter abbreviated as LAN) system employing a scan transmission system.

(Prior Art) In a LAN system, a message transmission method for exchanging data between stations and a scan transmission method for sharing necessary data between stations are generally adopted. In the former, the transmitting station specifies the receiving station and transmits data.
A station that has received data addressed to its own station writes the received data in a memory and performs data processing. A data transmission frame in this case is called a message frame.

On the other hand, in the latter, as shown in FIG. 3, a plurality of stations 2 (2a, 2b, 2c, 2d,...) Connected via a transmission line 1 each have a common memory 3, 3
Is divided into a plurality of blocks and assigned to each station 2. Then, each station 2 writes the required data in a block of the common memory 3 assigned to its own station, and transmits the data of the block by broadcast communication when transmitting from its own station. The other stations 2 that have received the transmission data by broadcast via the transmission path 1 update the contents of the blocks of the common memory 3 assigned to the transmission stations. Note that the data transmission frame in this case is called a scan frame.

For this reason, conventionally, each station 2 is provided with a data receiving device as shown in FIG. 4 so that data transmission and reception by these data transmission methods are performed smoothly.
In this data receiving apparatus, a data transmission frame transmitted via a transmission line 1 is received by a modem 4, converted into digital data, and transmitted to a transmission control circuit 5. The transmission control circuit 5 fetches only a received frame addressed to the own station or by broadcast communication, and writes it into the reception buffer memory 6. When the reception of the frame is completed, the first CPU (central processing unit) 7 is notified by transmitting a reception completion signal S. Upon receiving the reception completion notification, the first CPU 7 takes out the reception frame from the reception buffer memory 6 and determines whether the frame is a message frame or a scan frame. In the case of a message frame, the first CPU 7 stores the frame in the message transmission memory 8. The data is transferred, and in the case of a scan frame, is transferred to a corresponding block of the common memory 3 for scan transmission. Thus, the second CPU 9 takes out necessary data from the memory 8 and the common memory 3, interprets the contents, performs necessary data processing, and controls the operation.

However, in the above-described conventional apparatus, an expensive and large-scale microprocessor is used only for determining the type of the received frame and transferring the data based on the determination result. For this reason, the entire apparatus must be expensive, and circuit mounting has become complicated with the increase in peripheral circuits. In addition, if the data transmission speed is to be increased, the load on the transmission control circuit 5 becomes extremely large.

(Problems to be Solved by the Invention) As described above, in this type of conventional data receiving device, the entire device has to be expensive and the circuit mounting is complicated. Moreover, it has been very difficult to increase the data transmission speed.

Therefore, the present invention can reduce the cost of the entire apparatus and simplify the circuit implementation by omitting a microprocessor for merely determining the type of the received frame and transferring data based on the determination result. ,
An object of the present invention is to provide a data receiving apparatus that can easily realize a high data transmission speed.

[Structure of the Invention] (Means for Solving the Problems) In the present invention, each station has a common common memory, and the common memory is divided into a plurality of blocks and assigned to each station. Write the required data to the block assigned to its own station in its own common memory and transmit it incorporated in the frame, and when receiving a frame from another station, the block assigned to its own common memory transmitting station The present invention is applied to a data receiving device incorporated in each station in a network system adopting a scan transmission method for updating the content of the received frame with data of a received frame.

In order to solve the above problem, in the data receiving apparatus of the present invention, a frame type determining circuit that determines whether or not a corresponding frame is a scan frame for scan transmission from an identification code included in the received frame; A buffer memory for temporarily storing data of a frame determined as a scan frame by the frame type determination circuit among the received frames, an address generation circuit for generating an address for specifying a block of the transmitting station from the data of the received frame, and a buffer memory. And a transfer circuit for transferring the data stored in the common memory to a generated address in its own common memory.

(Operation) In the data receiving apparatus configured as described above, the frame type of the frame received by each station is determined by the frame type determination circuit, and only when the frame is a scan frame for scan transmission, The data of the received frame is temporarily stored in the buffer memory.

During a period when data is stored and held in the buffer memory, an address for specifying a block to be written in the common memory is generated by the address generation circuit. Then, the data stored and held in the buffer is written to a position specified by an address in the common memory by a transfer circuit such as a DMA circuit.

As described above, the buffer memory and the transfer circuit operate only for the scan frame for scan transmission in the frame type determination circuit, so that the time from receiving the scan frame to updating the content of the common memory can be reduced. .

(Embodiment) An embodiment in which the present invention is applied to each station 2 of the LAN system shown in FIG. 3 will be described below with reference to FIG. 1 and FIG.

FIG. 1 is a block diagram showing the overall configuration of a data receiving apparatus according to this embodiment. In the figure, the modem 11
The data of the data transmission frame transmitted via the transmission path 1 is converted into a digital signal. The received frame after the data conversion is output to the transmission control circuit 12 and the scan reception control circuit 13. The transmission control circuit 12 fetches only the message frame addressed to the own station from the received frames, and writes the data of the frame into the message transmission memory 14. On the other hand, the scan reception control circuit 13 fetches only the broadcast scan frame from the received frames, and rewrites the contents of the corresponding block of the scan transmission common memory 15 with the data of the frame. The CPU 16 takes out necessary data from the memory 14 and the common memory 15, interprets the contents, performs necessary data processing, and controls the operation.

FIG. 2 is a block diagram showing a specific configuration of the scan reception control circuit 13. As shown in FIG. As shown in the figure, the scan reception control circuit 13 detects a frame identification code included in a transmission frame, determines whether the frame is a message frame or a scan frame, and outputs a specified result to a serial / parallel conversion circuit 22 described later. And a frame type determination circuit 21 that notifies the frame check circuit 23, and converts the serial digital signal sent from the modem 11 into parallel data in response to being notified that the frame is a scan frame from the frame type determination circuit 21. The serial / parallel conversion circuit 22 that converts the data and sends it to the buffer memory 24 and the address generation circuit 25, which will be described later. If the frame type determination circuit 21 notifies that the scan frame is a scan frame, whether the scan frame is normally received Is checked, and the result is referred to as a DM as a transfer circuit described later. A
(Direct Memory Access) A frame check circuit 23 for notifying a circuit 26, a buffer memory 24 for temporarily storing parallel data sent from the serial / parallel conversion circuit 22, a serial / parallel conversion circuit
An address generation circuit 25 that extracts the data indicating the block number or address of the corresponding scan frame from the parallel data sent from 22 to generate a real address of the common memory 15 for scan transmission, When notified that the scan frame has been received, the DMA circuit 2 for transferring the contents of the buffer memory 24 to the scan transmission common memory 15 according to the address generated by the address generation circuit 25
6, etc.

In the present embodiment having such a configuration, when scan transmission is performed at each station 2 constructing a LAN, a station serving as a transmitting station transmits required data to a block assigned to its own station in a common memory 3 for scan transmission. Write to. Then, at the time of transmission of the own station, the data in the block is transmitted to other stations as a scan frame by broadcast communication. The other stations receive the frame data on the transmission path 1 via the modem 11, convert the data into digital signals, and take them into the transmission control circuit 12 and the scan reception control circuit 13. Here, since the received frame is a scan frame, when the frame type determination circuit 21 of the scan reception control circuit 13 determines that the frame is a scan frame, the subsequent data is serial data of the scan reception control circuit 13. / Parallel conversion circuit 22 converts the data to parallel
Is stored temporarily. Further, a block number and the like are extracted from the data of the received frame, and a real address on the common memory 15 is generated. Thereafter, the frame check sequence incorporated at the end of the received frame is checked by the frame check circuit 23, and when normal reception is determined, data in the buffer memory 24 is generated by the DMA circuit 26 by the address generation circuit 25. The data is transferred to the common memory 15 according to the real address. If the frame check circuit 23 determines that the frame is abnormally received, the received data is discarded.

On the other hand, when message transmission is performed at each station 2 that constructs the LAN, the station serving as the transmitting station stores the required data in the message transmission memory as in the conventional case.
Write to 14. Then, the data in the memory 14 is transmitted as a message frame by designating a receiving station. At the receiving station, the frame data on the transmission path 1 is received via the modem 11, converted into a digital signal, and taken into the transmission control circuit 12 and the scan reception control circuit 13. Here, since the received frame is a message frame addressed to the own station, the transmission control circuit
The next data is stored in the memory for message transmission 14
Is written to.

Thus, the data written in the common memory 15 and the memory 14 by the scan transmission or the message transmission is subjected to data processing by the CPU 16 and used for controlling various operations.

As described above, according to the present embodiment, the microprocessor and its peripheral circuits, which have conventionally been used only to determine whether the frame is a message frame or a scan frame and transfer data, are omitted, and the Control circuit 13
Is used, the following effects are obtained.

Since the buffer memory 24 incorporated in the scan reception control circuit 13 can be provided with a capacity capable of storing data for one frame, the scan reception control circuit 13 can be formed by one gate array. As a result, the cost of the entire device can be reduced, and the circuit mounting can be simplified.
Also, current consumption can be reduced.

Since the transmission control circuit 12 does not perform processing relating to the scan frame, the load is greatly reduced. As a result,
The process of the transmission control circuit 12 has a margin, and the data transmission speed can be increased within the operation range of the scan reception control circuit 13.

The time required to receive a scan frame and update the contents of the common memory 15 can be reduced by the amount of simplification of the circuit for handling the scan frame.

When two or more CPUs are used as in the past, software is complicated because data is exchanged between the CPUs. However, in this embodiment, the software is simple because only one CPU 16 is required, and the throughput is increased. I do.

The transmission control circuit 12 must be configured not to receive the scan frame, but since this scan frame is broadcast using the group address,
By changing the setting so that the transmission control circuit 12 does not accept the corresponding group address, a normal transmission control circuit including one LSI can be applied without changing the inside of the LSI.

Even if the scan frame has a variable length, it can be dealt with by configuring the DMA circuit 26 to detect the data length in the scan frame, if any, and to set the transfer number in the DMA circuit 26. Needless to say, a shift register can be used instead of the buffer memory 24, and a receiver can be used instead of the modem 11. other than this,
Of course, various modifications can be made without departing from the spirit of the present invention.

[Effects of the Invention] As described above in detail, according to the present invention, it is possible to omit a microprocessor for merely discriminating the type of a received frame and transferring data based on the judgment result. It is possible to provide a data receiving device which can reduce the cost and simplify the circuit mounting of the device, and can easily realize a high data transmission speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration in one embodiment of the present invention, FIG. 2 is a block diagram showing a specific configuration of a scan reception control circuit in the embodiment, and FIG.
FIG. 4 is a conceptual diagram showing a LAN (local area network) system, and FIG. 4 is a block diagram showing a conventional device. DESCRIPTION OF SYMBOLS 1 ... Transmission path, 2 ... Station, 11 ... Modem, 12 ... Transmission control circuit, 13 ... Scan reception control circuit, 14 ... Message transmission memory, 15 ... Scan transmission common memory, 16 ……CPU.

Claims (1)

(57) [Claims] 1. Each station has a common memory in common, and the common memory is divided into a plurality of blocks and assigned to each station, and each station transfers necessary data to its own station in its own common memory. Scan transmission to write to the allocated block, transmit it incorporated in the frame, and when receiving a frame from another station, update the contents of the block allocated to the transmitting station of its own common memory with the data of the received frame. A data receiving device incorporated in each of the stations in the network system adopting a system, a frame type determination circuit that determines whether the corresponding frame is a scan frame for scan transmission from an identification code included in the received frame, Of the received frame A buffer memory for temporarily storing data of a frame determined as a scan frame by the frame type determination circuit; an address generation circuit for generating an address for specifying a block of the transmission station from the data of the received frame; A transfer circuit for transferring data stored in a memory to the generated address in the own common memory.