JP2003203064A - Microcomputer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microcomputer capable of rewriting a built-in flash memory by utilizing a generally used PROM writer. <P>SOLUTION: This microcomputer 1 is provided with a central processor 10 and the electrically writable flash memory FMRY2 on one semiconductor base, and has a first operation mode operated in accordance with the command inputted from an external device 30. When a read command for reading out the information stored in the flash memory from the external device is inputted to the microcomputer in the first operation mode, the central processor is separated from a bus. Whereby the external device can freely read large volumes of flash memory built in the microcomputer on the basis of the read command in accordance with its specification. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data processing device having an electrically rewritable non-volatile flash memory built-in, and the built-in flash memory can be used as an external device such as a PROM writer as well as a single flash memory. The present invention relates to a rewritable technology, for example, a technology effectively applied to a microcomputer.

[0002]

2. Description of the Related Art JP-A-1-161469 discloses an EPROM (erasable and programmable read only memory) or an EEPROM (electrically erasable and programmable read only memory) as a programmable nonvolatile memory. -A memory) is mounted on a single semiconductor chip. Programs and data are held in a non-volatile memory which is on-chip in such a microcomputer. Since the EPROM erases stored information by ultraviolet rays, rewriting cannot be performed without removing it from the mounting system. Since the EEPROM can be electrically erased and written, its stored information can be rewritten in the state where it is mounted in the system. However, the memory cell constituting the EEPROM is MNOS (Metal Nitride Oxide). Since a selection transistor is required in addition to a memory element such as a semiconductor, the size is, for example, about 2.5 to 5 times that of an EPROM memory cell, and a relatively large chip occupation area is required. To do.

Japanese Unexamined Patent Publication No. 2-289997 discloses a batch erase type EEPROM. This collective erasing type EEPROM can be understood in the same meaning as the flash memory in this specification. A flash memory can rewrite information by electrical erasing / writing, and like the EPROM, its memory cell can be configured by one transistor, and all the memory cells can be collectively or It has a function to electrically erase all blocks. Therefore, the flash memory can rewrite the stored information in a state where it is mounted on the system (onboard), and can shorten the rewriting time by its batch erasing function, and further, it can reduce the chip occupation area. It also contributes to reduction.

[0004]

The present inventor has studied a microcomputer equipped with a flash memory. A microcomputer with a built-in flash memory is capable of on-board rewriting, but considering the user's usage, initial writing is not on-board, but using a writing device such as a PROM writer before board mounting. It may be more efficient to write it. Therefore,
Even in such a microcomputer with a built-in flash memory, it is connected to a writing device generally used for writing in EPROM or EEPROM such as a PROM writer via a socket adapter, and supports a function writable by the writing device. I found the need for that. At this time, the writing and erasing of the flash memory is performed by the EP
Complex control is required as compared with ROM and EEPROM. In particular, in the case of erasing, over-erasing, which is a problem peculiar to flash memory (if erasing too much, the threshold voltage of the memory cell transistor becomes too small and becomes negative,
In order to avoid such a phenomenon that normal reading cannot be performed), it is necessary to perform an erasing method such as pre-writing for equalizing the write level before erasing or erasing little by little while performing verification. It is unreasonable to entrust the control procedure for such processing to the general-purpose PROM writer side, and it is not realistic to deal with it with a writing device such as a PROM writer dedicated to a microcomputer with a built-in flash memory. .

An object of the present invention is to provide PRO before mounting on a circuit board.
An object of the present invention is to provide a data processing device with a built-in flash memory, which is easy to use when writing information using an external device such as an M writer. Another object of the present invention is to provide a data processing device capable of rewriting the built-in flash memory by utilizing an external device such as a PROM writer which is used for general purposes. Further, at this time, it is another object of the present invention to provide a data processing device which suppresses an increase in the circuit scale to be newly built in for writing information by an external device as much as possible.

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

[0007]

The outline of the representative one of the inventions disclosed in the present application will be briefly described as follows.

That is, a central processing unit and an electrically rewritable non-volatile flash memory are included in one semiconductor substrate, and an operation mode for rewriting the built-in flash memory according to an instruction of an external device is provided, A command latch unit that is externally writable in a state where the operation mode is set, a command analysis unit that analyzes the command latched therein, and a procedure for rewriting the flash memory according to the analyzed content. A data processing device is configured by including control means for performing control.

While the flash memory is being rewritten by the external device, the built-in central processing unit does not necessarily have to perform another process, and may be in a sleep state substantially. At this time, by causing the built-in central processing unit to execute the processing by the command analysis means and the control means, the dedicated circuit for rewriting such as the command analysis means and the control means is reduced.

An external device such as an EPROM writer used for general purposes is a target including at least a flash memory for applying a high voltage for rewriting to a non-volatile memory element and for writing an address and data for rewriting according to a write signal. It is designed to be supplied to a semiconductor device (LSI). Such an external device supplies commands, data, and addresses asynchronously with the central processing unit incorporated in the data processing device. Therefore, there is provided flag means for indicating that a command has been written in the command latch means, and data latch means that is externally writable in place of the command latch means when the flag means indicates the command latch state. And an address latching means capable of writing address information from the outside, thereby preventing a collision between a command and data information written in a different cycle from the external device on the latching means, and the central processing unit. Is for reading the command of the command latch means based on the command latch state of the flag means.

If the control of the flag means is also entrusted to the central processing unit, the central processing unit must activate the bus cycle and constantly monitor the contents of the command latching means, resulting in a waste of operation. Therefore, a command decoder is provided which decodes the latch contents of the command latch means and decodes the predetermined command to set the flag means to the command latch state.

If the central processing unit analyzes all the latched commands, the operation instructed by the commands may not meet the timing. For example, it is a read command for reading data from the flash memory. In order to deal with this, the command latch means, the data latch means, and the address latch means are connected to the flash memory and the central processing unit, and the command latch means, the data latch means, and the address latch means are connected to the flash memory. A state in which the central processing unit is not connected to the central processing unit is provided in the internal bus with selectable gate means, and the gate means is generated by the command decoder by decoding a command other than the predetermined command. Be controlled by signals. When the gate means is open, the flash memory can be directly read-accessed from the outside of the data processing device. The read command is a command other than the predetermined command.

The procedure control program for rewriting the flash memory to be executed by the central processing unit is stored in advance in the flash memory, and the program is transferred to the RAM in response to the setting of the rewriting operation mode by the external device. However, the program transferred to the RAM can be executed by the central processing unit.

Considering that the amount of information to be stored in the flash memory differs depending on the type of information, such as a program, a data table, and control data, depending on the application, after mounting on a system (circuit board). In order to improve the rewriting efficiency by eliminating the waste of the write operation after collectively erasing the memory block in accordance with the partial or partial rewriting of the information held in the built-in flash memory, the batch erasing in the flash memory is possible. As a unit, a plurality of memory blocks having different storage capacities may be allocated.

[0015]

According to the above-mentioned means, the realization of the rewriting sequence according to the command asynchronously given from the external device by the built-in circuit means that the data information is given to the external device before the data information and the address information are given. The command can be given to the data processing device in the same manner as described above, and information can be written to the built-in flash memory of the data processing device by connecting to a general-purpose-used external device such as a PROM writer via a socket adapter. To

The control of the rewriting sequence instructed by the command by the built-in central processing unit eliminates or eliminates the dedicated circuit for the control, and realizes the reduction of the chip area of the data processing unit. Furthermore, the control sequence for rewriting can be changed by the software that the central processing unit should execute, which enables setting of conditions such as the write time according to the characteristics of the storage elements that make up the flash memory. .

[0017]

EXAMPLES Examples of the present invention will be described in accordance with the following items. [1] Principle of flash memory [2] Multiple memory blocks with different storage capacities [3] Principle of command-based information writing by PROM writer [4] Microcomputer [5] Built-in flash memory [6] Command-compatible hardware Wear [7] Command specifications such as information writing by PROM writer [8] On-board information writing

[9] Information writing operation by command method (command correspondence) [10] Operation of PROM writer at information writing by command method [11] CPU operation at information writing by command method [12] Single unit of writing specification by PROM writer Compatibility with flash memory LSI

[1] Principle of flash memory

FIG. 31 shows the principle of the flash memory. The memory cell exemplarily shown in FIG.
It is composed of an insulated gate field effect transistor having a layer gate structure. In the figure, 1 is a P-type silicon substrate, 2 is a P-type semiconductor region formed on the silicon substrate 1, and 3 and 4 are N-type semiconductor regions. 5 is a floating gate formed on the P-type silicon substrate 1 via a thin oxide film 6 (for example, 10 nm thick) as a tunnel insulating film, and 7 is formed on the floating gate 5 via an oxide film 8. It is a control gate. The source is constituted by 4, and the drain is constituted by 3, 2. The information stored in this memory cell is substantially held in the transistor as a change in threshold voltage. Hereinafter, unless otherwise stated, in the memory cell,
A case where a transistor for storing information (hereinafter also referred to as a memory cell transistor) is an N-channel type will be described.

The operation of writing information to the memory cell is realized, for example, by applying a high voltage to the control gate 7 and the drain and injecting electrons from the drain side to the floating gate 5 by avalanche injection. By this write operation, the memory transistor is changed to the one shown in FIG.
As shown in FIG. 5, the threshold voltage seen from the control gate 7 becomes higher than that of the memory transistor in the erased state in which the write operation is not performed.

On the other hand, the erase operation is realized, for example, by applying a high voltage to the source and extracting electrons from the floating gate 5 to the source side by the tunnel phenomenon.
As shown in FIG. 31B, the threshold voltage seen from the control gate 7 of the memory transistor is lowered by the erase operation. In FIG. 31B, the threshold voltage of the memory cell transistor is set to a positive voltage level in both the write and erase states. That is, the threshold voltage in the written state is raised and the threshold voltage in the erased state is lowered with respect to the word line selection level applied from the word line to control gate 7. By having such a relationship between both threshold voltages and the word line selection level, it is possible to configure a memory cell with one transistor without employing a selection transistor. In the case of electrically erasing the stored information, the stored information is erased by pulling out the electrons accumulated in the floating gate 5 to the source electrode. Therefore, if the erase operation is continued for a relatively long time, the write operation is performed. More electrons than the amount of electrons injected into the floating gate 5 during operation will be extracted. Therefore, when over-erasing is performed such that electrical erasing is continued for a relatively long time, the threshold voltage of the memory cell transistor becomes, for example, a negative level, and is selected even at the non-selected level of the word line. Cause Note that writing can be performed by utilizing a tunnel current as in the case of erasing.

In the read operation, the voltages applied to the drain and the control gate 7 are compared so that weak writing to the memory cell, that is, undesired carrier injection to the floating gate 5 is not performed. Restricted to very low values. For example, a low voltage of about 1 V is applied to the drain and a low voltage of about 5 V is applied to the control gate 7. By detecting the magnitude of the channel current flowing through the memory cell transistor by these applied voltages, the logical values "0" and "1" of the information stored in the memory cell can be determined.

FIG. 32 shows the principle of construction of a memory cell array using the memory cell transistors. In the figure, four memory cell transistors Q1 to Q4 are shown as representatives. In the memory cells arranged in a matrix in the X and Y directions, the memory cell transistors Q arranged in the same row
1, Q2 (Q3, Q4) control gates (memory cell selection gates) are respectively associated with corresponding word lines WL.
1 (WL2), and the drain regions (memory cell input / output nodes) of the memory transistors Q1, Q3 (Q2, Q4) arranged in the same column are connected to the corresponding data lines DL1 (DL2), respectively. There is. The source regions of the storage transistors Q1, Q3 (Q2, Q4) are coupled to the source line SL1 (SL2).

FIG. 33 shows an example of voltage conditions for the erase operation and the write operation for the memory cell. In the figure, the memory element means a memory cell transistor, and the gate means a control gate as a selection gate of the memory cell transistor. In the figure, in the negative voltage type erasing, a high electric field necessary for erasing is formed by applying a negative voltage such as −10 V to the control gate. As is clear from the voltage conditions illustrated in the figure, in the case of erasing by the positive voltage method, it is possible to carry out batch erasing at least for the memory cells whose sources are commonly connected. Therefore, in the configuration of FIG. 32, if the source lines SL1 and SL2 are connected, the four memory cells Q1 to Q4 can be collectively erased. In this case, the size of the memory block can be arbitrarily set by changing the number of memory cell transistors connected to the same source line. In the source line division method, in addition to the case where the data line as shown in FIG. 32 is used as a unit (the common source line is extended in the data line direction), the case where the word line is used as a unit (the common source line) Is extended in the word line direction). On the other hand, in the erase of the negative voltage system, it is possible to collectively erase the memory cells to which the control gates are commonly connected.

[2] Forming a plurality of memory blocks with different storage capacities

FIG. 34 shows a circuit block diagram of an example of a flash memory in which the memory capacities of the memory blocks that can be erased collectively are different.

Flash memory FMRY shown in FIG.
1 has 8-bit data input / output terminals D0 to D7,
Memory arrays ARY0 to ARY for each data input / output terminal
7 is provided. Although not particularly limited, the memory arrays ARY0 to ARY7 are divided into two, a memory block LMB having a relatively large storage capacity and a memory block SMB having a relatively small storage capacity. Although the details of the memory array ARY0 are representatively shown in the drawing, the other memory arrays ARY1 to ARY7 are similarly configured.

In each of the memory arrays ARY0 to ARY7, a memory cell M composed of the insulated gate field effect transistor having the two-layer gate structure described with reference to FIG.
Cs are arranged in a matrix. In the figure, WL0
WLn is a word line common to all the memory arrays ARY0 to ARY7. The control gates of the memory cells arranged in the same row are connected to the corresponding word lines. In each of the memory arrays ARY0 to ARY7, the drain regions of the memory cells MC arranged in the same column are connected to the corresponding data lines DL0 to DL7. The source regions of the memory cells MC forming the memory block SMB are commonly connected to the source line SL1, and the source regions of the memory cells MC forming the memory block LMB are commonly connected to the source line SL2.

The source lines SL1 and SL2 are supplied with the high voltage Vpp used for erasing from the voltage output circuits VOUT1 and VOUT2. Voltage output circuit VOUT1, VO
The output operation of UT2 is selected by the values of bits B1 and B2 of the erase block designation register. For example, by setting "1" to the bit B1 of the erase block designating register, only the small memory blocks SMB of the memory arrays ARY0 to ARY7 can be collectively erased. When "1" is set to the bit B2 of the erase block designation register, only the large memory block LMB of each memory array ARY0 to ARY7 can be collectively erased. When "1" is set to both bits B1 and B2, the entire flash memory can be erased at once.

The word lines WL0 to WLn are selected by X
Address buffer XABUFF and X address latch X
X address signal AX taken in via ALAT
It is performed by decoding by the address decoder XADEC. The word driver WDRV drives the word line based on the selection signal output from the X address decoder XADEC. In the data read operation, the word driver WDRV is supplied with 5V supplied from the voltage selection circuit VSEL.
Is operated by using a voltage Vcc like this and a ground potential like 0V as a power source, a word line to be selected is driven to a selection level by the voltage Vcc, and a word line to be deselected is not connected to a ground potential such as ground potential. Maintain the selected level. In the data write operation, the word driver WDRV
It operates by using a voltage Vpp such as 12V supplied from the voltage selection circuit VSEL and a ground potential such as 0V as a power source, and drives a word line to be selected to a high voltage level for writing such as 12V. In the data erasing operation, the output of the word driver WDRV is set to a low voltage level such as 0V.

In each of the memory arrays ARY0 to ARY7, the data lines DL0 to DL7 have a Y selection switch Y.
It is commonly connected to the common data line CD via S0 to YS7. The switch control of the Y selection switches YS0 to YS7 is
This is performed by the Y address decoder YADEC decoding the Y address signal AY fetched through the Y address buffer YABUFF and the Y address latch YALAT. The output selection signal of the Y address decoder YADEC is commonly supplied to all the memory arrays ARY0 to ARY7. Therefore, the Y address decoder YADEC
By setting any one of the output selection signals of 1 to the selection level, one data line is connected to the common data line CD in each of the memory arrays ARY0 to ARY7.

The data read from the memory cell MC to the common data line CD is given to the sense amplifier SA via the selection switch RS, amplified there, and then outputted from the data output buffer DOB to the outside via the data output latch DOL. Is output. The selection switch RS is set to the selection level in synchronization with the read operation. The write data supplied from the outside is held in the data input latch DIL via the data input buffer DIB. When the data held in the data input latch DIL is "0", the write circuit WR supplies a high voltage for writing to the common data line CD via the selection switch WS. This high voltage for writing is applied to the X line through the data line selected by the Y address signal AY.
The address signal AX is supplied to the drain of the memory cell to which a high voltage is applied to the control gate, so that the memory cell is written. The selection switch W
S is set to the selection level in synchronization with the writing operation. The write / erase control circuit WECONT generates various timings of write / erase and selection control of voltage.

A flash memory FMRY1 according to the application
Considering that the amount of information to be stored in the flash memory differs depending on the type of the information, such as a program, a data table, control data, etc., the storage capacities are mutually different as batch erasable units in the flash memory. By configuring a plurality of memory blocks SMB, LMB, after mounting the microcomputer on the circuit board,
It is possible to improve the rewriting efficiency by eliminating the waste of the writing operation after collectively erasing the memory blocks in accordance with the partial or partial rewriting of the held information in the microcomputer built-in flash memory.

[3] Command-based information writing principle by PROM writer

FIG. 1 shows the flash memory F as described above.
In the microcomputer MCU1 according to the first embodiment having the built-in MRY2, the built-in flash memory is
A functional block diagram of rewriting processing by the ROM writer is shown.

As a circuit module sharing the internal bus BUS, a central processing unit (hereinafter also simply referred to as a CPU) 10, a flash memory FMRY2, and a control circuit 20 are typically shown in FIG. This microcomputer M
The CU1 has a write mode by the PROM writer 30. For example, when the microcomputer MCU1 is coupled to a predetermined terminal of the PROM writer 30 via a socket adapter (not shown), the mode terminal (not shown) of the microcomputer MCU1 is forcibly set to a predetermined level,
The operation mode of the microcomputer MCU1 is PROM
The writing mode by the writer 30 is set. In such an operation mode, the CPU 10 is disconnected from the internal bus BUS via a bus switch (not shown). Control circuit 2
Reference numeral 0 indicates a command latch means 21 which is writable by the PROM writer 30 in a state where the write operation mode by the PROM writer 30 is set, a command analysis means 22 which analyzes a command latched by the command latch means 21, and analyzed contents. And sequence control means 23 for performing procedure control for rewriting the flash memory according to the above.
The PROM writer 30 supplies predetermined commands such as erase (erase), erase verify, program (write), and program verify, and subsequently supplies necessary data information and address information. The command supplied from the PROM writer 30 is interpreted by the control circuit 20, and the sequence control means 23 provides the flash memory FMRY2 with a control signal for writing using the necessary data information and address information.

The realization of the rewriting sequence in accordance with the command given from the PROM writer 30 by the built-in control circuit 20 is similar to the case of giving the data information before giving the data information and the address information to the PROM writer 30. It suffices to give a command to the computer MCU1, and the microcomputer MCU is connected to the PROM writer 30 used for general purpose via a socket adapter.
Information can be written in the flash memory FMRY2 incorporated in the microcomputer by combining 1s. In this configuration, the microcomputer MCU1 in which the write mode by the PROM writer 30 is set is regarded as the same flash memory chip by the PROM writer 30.

FIG. 2 shows the flash memory FMRY2.
A microcomputer M according to a second embodiment having a built-in
In the CU2, the built-in flash memory MRY2 is set to P
A functional block diagram when the rewriting process is performed by the ROM writer 30 is shown.

Microcomputer MC shown in FIG.
U2 reduces the dedicated circuit for rewriting such as the command analysis means 22 and the sequence control means 23 by causing the built-in CPU 10 to execute the command analysis and sequence control by the control circuit 20.
As is apparent from the fact that the CPU 10 is disconnected from the internal bus BUS in the write operation mode by the PROM writer 30 in FIG. 1, the PROM writer 3
During rewriting of the flash memory FMRY2 by 0, the built-in CPU 10 does not necessarily have to perform another process, and may be in a sleep state substantially. In FIG. 2, such a built-in CPU 10 is effectively used.

In the figure, a CPU 10 and a flash memory FMR are provided as circuit modules sharing the internal bus BUS.
Y2 and the command latch means 21 are representatively shown. This microcomputer MCU2 has a writing mode by the PROM writer 30. For example, a microcomputer MC via a socket adapter (not shown)
If U2 is connected to a predetermined terminal of the PROM writer 30,
A mode terminal (not shown) of the microcomputer MCU2 is forcibly set to a predetermined level to set the write mode by the PROM writer 30. In such an operation mode, the PROM writer 30 is not particularly limited, but the CPU
In order not to compete with the internal bus access by 10, the internal bus is not directly supplied with data information or address information. The data information and address information are written in a data latch and address latch (not shown) similar to the command latch means 21. The CPU 10 uses the PRO
In the state where the write operation mode by the M writer 30 is set, the command analysis means 22 for analyzing the command written from the PROM writer 30 and the procedure control for rewriting the flash memory FMRY2 according to the analyzed contents are performed. The function of the sequence control means 23 is realized together with an operation program therefor. PROM writer 3
0 supplies a predetermined command such as erase (erase), erase verify, program (write), and program verify, and subsequently supplies necessary data information and address information. The command supplied from the PROM writer 30 is interpreted by the CPU 10, and C is read accordingly.
The PU 10 gives a control signal for writing to the flash memory FMRY2 by using necessary data information, address information and the like.

FIG. 3 shows an example of command writing timing by the PROM writer 30. In the figure, the cycle described as command writing is the PROM writer 3.
This is a write cycle of 0 to the microcomputer MCU2. First, a command is written in the command latch means 21, and then data information and address information are written in a data latch and an address latch (not shown) as needed. In the figure, the cycle described as a write cycle is an information write cycle of the flash memory which is controlled by the CPU according to the content written by the PROM writer 30.

FIG. 4 shows an example of the timing of the information write cycle of the flash memory under the control of the CPU.
This write cycle is a command analysis cycle by the CPU 10, a write cycle that is actually performed on the flash memory according to the command analysis result, and a post-processing cycle.

Microcomputer MCU2 of this embodiment
Also, by connecting the PROM writer 30 which is used for general purpose in the same manner as in the above embodiment, through the socket adapter,
Microcomputer built-in flash memory FMRY2
Information can be written to. In addition, the rewriting sequence instructed by the command CP
Since U10 controls, a dedicated circuit for the control is unnecessary or eliminated, and the chip area of the microcomputer MCU2 is reduced. Furthermore, since the control sequence for rewriting can be changed by software to be executed by the CPU 10, it is possible to set conditions such as the write time according to the characteristics of the memory cell transistors forming the flash memory FMRY2. The difference in effect between the first embodiment and the second embodiment is shown collectively in FIG.

[4] Microcomputer

FIG. 6 is a block diagram showing a more detailed embodiment of the microcomputer MCU3 corresponding to the microcomputer shown in FIG.

Microcomputer MC shown in FIG.
U3 is a CPU 10, a flash memory FMRY2, a serial communication interface SCI,
Control circuit CONT and random access memory R
AM, 16-bit integrated timer pulse unit IPU, watchdog timer WDTMR,
Ports PORT1 to PORT12, clock oscillator C
PG, interrupt controller IRCONT, analog
The digital converter ADC and the weight state controller WSCONT are provided, and the circuit modules thereof are not particularly limited, but are formed on one semiconductor substrate such as silicon by a known semiconductor integrated circuit manufacturing technique.

CPU 10, flash memory FMR
Y2, random access memory RAM, and 16-bit integrated timer pulse unit I
PU is an address bus ABUS and a lower data bus LDB
US (for example, 8 bits) and upper data bus HDBU
It is connected to S (for example, 8 bits). Serial communication interface SCI, watchdog timer WDTMR, interrupt controller IRCON
T, analog / digital converter ADC, weight state controller WSCONT, and port PORT1
The PORT 12 is connected to the address bus ABUS and the upper data bus HDBUS.

In FIG. 6, Vpp is a high voltage for rewriting the flash memory FMRY2. EXTAL and X
TAL is an oscillator (not shown) externally attached to the chip of the microcomputer MCU3, and is the clock oscillator CP.
This is a signal given to G. φ is the clock oscillator CPG
Is a synchronous clock signal output from the outside. RES
* (Symbol * means that the signal with this is a low enable signal) is a reset signal, STBY * is a standby signal, and is supplied to the CPU 10 and other circuit blocks. NMI is a non-maskable interrupt signal and gives a non-maskable interrupt to the interrupt controller IRCONT. Other interrupt signals not shown are ports PORT8, PORT
It is given to the interrupt controller IRCONT via 9. AS * is an address strobe signal indicating the validity of the address signal output to the outside, RD * is a read signal notifying the outside that it is a read cycle, and HWR * is an outside indicating that it is a write cycle of the upper 8 bits. The upper byte write signal for notifying, LWR *, is a lower byte write signal for notifying externally that it is a write cycle of the lower 8 bits, and these are used as access control signals to the outside of the microcomputer MCU3.

MD0 to MD2 are control circuits CON for setting the operation mode of the microcomputer MCU3.
This is a mode signal supplied to T. The operation mode set by this is not particularly limited, but an operation mode relating to an address space that can be managed by the CPU, such as a maximum mode or a minimum mode, a PROM writer 30
The operation mode (hereinafter also simply referred to as a PROM writer write mode) that enables the writing of information in the built-in flash memory FMRY2 by means of. In contrast to such a PROM writer write mode, in the maximum mode and the minimum mode, the CPU 10 is a microcomputer MCU.
Built-in flash memory FMRY2 in 3 on-board state
Can be understood as an operation mode that enables rewriting.

A PROM writer 30 using a command system
There is no particular limitation on the input / output of the data BD0 to BD15 for the microcomputer MCU3 to access the outside except the operation mode for writing information to the flash memory FMRY2.
1, PORT2 are assigned. Although not particularly limited, the ports PORT3 to PORT5 are assigned to the outputs of the address signals BA0 to BA19 at this time.

On the other hand, when the PROM writer rewriting mode is set in the microcomputer MCU, the connection with the PROM writer 30 for rewriting the flash memory FMRY2 is not particularly limited, but the ports PORT2 to PORT5 and PORT8 are not limited. Assigned. That is, the port PORT2 is assigned to the input / output of the data ED0 to ED7 for command writing and writing / verifying, and the address signal E
Input of A0 to EA16 and access control signal CE
Inputs of * (chip enable signal), OE * (output enable signal), and WE * (write enable signal) to the ports PORT3 to PORT5 and POR
T8 is assigned. The chip enable signal CE *
Is a chip selection signal from the PROM writer 30, the output enable signal OE * is an instruction signal of an output operation to the microcomputer MCU3, and the write enable signal WE * is a microcomputer MCU3.
Is a signal for instructing a write operation to the. The input terminal of the signal NMI is assigned to the input of the 1-bit EA9 of the address signals EA0 to EA16. The external terminals of the ports allocated in this way, and the high voltage V
Other necessary external terminals such as a pp application terminal are connected to the PROM writer 30 via a socket adapter (not shown) as a socket for pin arrangement conversion. PR above
The external terminal group of the microcomputer MCU3 assigned for connection with the PROM writer 30 in the OM writer rewriting mode is assigned another function in other operation modes.

FIG. 7 shows the microcomputer MC of FIG.
The upper surface of a package having external terminals on four sides obtained by sealing U3 with resin, for example, is shown. The signals shown in FIG. 7 are common to those in FIG. External terminals (pins) without signal names are input pins for wait signals, input pins for bus request signals, output pins for bus acknowledge signals, serial communication
It is used for peripheral circuit such as interface SCI and external signal input / output pin.

[5] Built-in flash memory

FIG. 8 shows the microcomputer MC of FIG.
An overall block diagram of the flash memory FMRY2 built into U3 is shown. In the same figure, ARY is a memory array in which memory cells constituted by the insulated gate field effect transistors of the two-layer gate structure described in FIG. 31 are arranged in a matrix. This memory array AR
As for Y, the control gates of the memory cells are connected to the corresponding word lines, the drain regions of the memory cells are connected to the corresponding data lines, and the source regions of the memory cells are the memory blocks. Each of them is connected to a common source line, but the division mode of the memory block is different from that in FIG. For example, as shown in FIG. 9, seven large memory blocks (large blocks) LMB0 to LMB6 with relatively large storage capacities and 8 with relatively small storage capacities respectively.
Small memory blocks (small blocks) SMB0 to SM
It is divided into B7. The large memory block is used as a program storage area or a large capacity data storage area. The small memory block is used as a small capacity data storage area.

In FIG. 8, AIL is an address signal PA.
It is a latch circuit of B0 to PAB15. The address signals PAB0 to PAB15 correspond to the output address signal of the CPU 10 and, in the PROM writer rewriting mode, the output address signal EA0 of the PROM writer 30.
To EA15. XADEC is an X address decoder which decodes an X address signal fetched through the address latch AIL. The word driver that drives the word line based on the selection signal output from the X address decoder XADEC is not shown. In the data read operation, the word driver drives the word line with a voltage such as 5V, and in the data write operation, drives the word line with a high voltage such as 12V. All the outputs of the word driver are 0 in the data erasing operation.
It is brought to a low voltage level such as V. YADEC is a Y address decoder that decodes a Y address signal fetched through the address latch AIL. YSEL is a Y selector that selects a data line according to the output selection signal of the Y address decoder YADEC. SA is a sense amplifier that amplifies a read signal from the data line selected by the Y selector YSEL in the data read operation. DO
L is a data output latch that holds the output of the sense amplifier SA. DOB is a data output buffer for outputting the data held by the data output latch DOL to the outside. In the figure, PDB0 to PDB7 are lower 8-bit (1 byte) data, and PDB8 to PDB15 are higher 8-bit (1 byte) data. According to this example, the maximum output data is 2 bytes. The DIB is a data input buffer for fetching write data supplied from the outside. The data input from the data input buffer DIB is held in the data input latch DIL. The data held in the data input latch DIL is "
When it is "0", the write circuit WR supplies a high voltage for writing to the data line selected by the Y selector YSEL. This high voltage for writing is the drain of the memory cell to which the high voltage is applied to the control gate according to the X address signal. Then, the memory cell is written by this, and EC is an erase circuit for supplying a high erase voltage to the source line of the specified memory block to erase the memory blocks in batch. The erase block is designated by the erase block designation register MBREG, and the CPU 10 writes data to the register MBREG.

FCONT is a flash memory FMRY.
2 is a control circuit for performing timing control of data read operation in 2 and selection control of various timings and voltages for writing and erasing. This control circuit FCONT is
The processing is performed by referring to the contents of the control register CREG.

FIG. 10 shows the control register CR.
An example of EG and erase block designation register MBREG is shown. This erase block designation register MBREG is 2
It is composed of book registers MBREG1 and MBREG2, and each register CREG, MBREG1, M
BREG2 is an 8-bit register. In the control register CREG, Vpp is a high voltage application flag that is set to "1" in response to the application of the high voltage for rewriting.
The E bit is a bit instructing an erase operation, and the EV bit is an instruction bit for a verify operation in erase. The P bit is an instruction bit for a write operation (program operation), and the PV bit is an instruction bit for a verify operation in writing. Erase block designation register M
BREG1 and MBREG2 are registers for designating which memory block contained in a large block divided into 7 and a small block divided into 8 is to be erased. For example, bit "1" means selection of the corresponding memory block, and bit "0" means non-selection of the corresponding memory block. For example, when the seventh bit of the erase block designating register MBREG2 is "1", erasing of the small memory block SMB7 is designated.

The registers CREG, MBREG1, M
The BREG 2 is readable and writable by the CPU 10. The control circuit FCONT has its register CR
The setting contents of EG, MBREG1 and MBREG2 are referred to, and erasing / writing is performed according to them. CPU
10 is the register CREG, MBREG1, MBR
By rewriting the contents of EG2, the erase / write operation can be controlled. For example, the PROM
When the writer rewrite mode is set, the CPU 10
According to the contents of the command written in the command latch by the PROM writer 30.
G, MBREG1, and MBREG2 will be set.

In FIG. 8, the control circuit FCONT includes
FLM, MS-FLN, MS-MIS as control signal
N, M2RDN, M2WRN, MRDN, MWRN, I
OWORDN, RST, VPPH, A9H, SECS
N, SECN, DSCN, and XMON are provided.

The control signal FLM is the flash memory FM.
The signal is a signal designating the operation mode of RY2, and is set to a logical value "1" when the microcomputer MCU3 is coupled to the PROM writer 30 to be rewritable, and is set to a logical value "0" when it is yes. This signal FL
M is formed based on the mode signals MD0 to MD2, for example. The control signal MS-FLN is a selection signal for the flash memory FMRY2. Control signal MS-MI
SN is register CREG, MBREG1, MBREG2
Selection signal. Register CREG, MBREG1,
Which of the MBREG2 is selected is determined by the lower 2 bits of the address signal output from the CPU 10. M2RD
N is a memory read strobe signal, M2WRN is a memory write strobe signal, MRDN is a read signal of the control register CREG, and MWRN is a write signal of the control register CREG. Memory write strobe signal M2WRN is regarded as a strobe signal for writing data to be written in the memory cell into data input latch DIL. The actual writing to the memory cell is started by setting the P bit in the control register CREG. The control signal IOWORDN is a signal for switching between 8-bit read access and 16-bit read access to the flash memory FMRY2. The control signal RST is a reset signal for the flash memory FMRY2. The flash memory FMRY2 is reset by this signal RST, or the Vpp flag of the control register CREG is set to "".
When set to 0 ", the EV, PV, E, and P mode setting bits in the register CREG are cleared. VPPH is a detection signal of Vpp = 12V.
Other signals A9H, SECN, DSCN, XMO
Each of the N signals is a security bit enable signal or a test enable signal and is not directly related to the present invention, and therefore its detailed description is omitted.

[6] Command system compatible hardware

FIG. 11 shows a detailed example of hardware for coping with the PROM writer rewriting mode by the command system in the microcomputer of FIG.

Since the command and address supplied from the PROM writer 30 are input asynchronously with the CPU 10, the command latch CL for receiving the command,
An address latch AL for receiving an address is provided. Port POR connected to PROM writer 30
T is uniquely determined via a socket adapter (not shown). When the port PORT has a register, the register can be used as the address latch AL or the command latch CL, and it is not necessary to newly provide them. Further, a command flag CF is assigned to a predetermined bit of the command latch CL so that the CPU 10 can recognize that the command has been written in the command latch CL. CPU 1 when command flag CF is set
0 knows that a command has been input to the command latch CL, and performs an operation of reading the command. PRO
The writing from the M writer 30 is first a command writing, and then the address and data are written from the PROM writer 30 as needed. At this time, since the time from the command input to the data input is as short as 20 ns, the data may be input to the command latch CL earlier than the CPU 10 goes to read the command. Therefore, in order to avoid a command-data collision, another data latch DL for receiving data is provided in addition to the command latch CL. Further, a data flag DF indicating that data is input to the data latch DL
Is assigned to a predetermined bit of the command latch. CPU1
0 is CF = 1 at the beginning (command has already been input)
Alternatively, when DF = 1 (a command is input and data is also input), the command is read, and when DF = 1 after command recognition, the data is read.

Here, two latches, a command latch CL and a data latch DL, are used for data input / output port PORT.
Since it is shared, it is necessary to identify the command and data input from the PROM writer 30. Therefore, the input data from the PROM writer 30 is latched in the command latch CL when CF = 0 and DF = 0, and C
The data latch DL is latched when F = 1 and DF = 0. That is, as conceptually shown in FIG. 11, a latch control signal is generated by receiving signals corresponding to respective logical values of the write signal WE, the command flag CF, and the data flag DF from the PROM writer 30. A gate AND is provided. Furthermore, FIG.
, The command decoder DEC decodes the type of command latched in the command latch CL, sets the command flag CF when the command is a predetermined command, and the data latch DL stores data. The logic is employed to set the data flag DF and clear the command flag CF when latched.
As a result, the command latch CL and the data latch D
The proper use of L is realized. According to this embodiment, the command latch CL is an 8-bit register, the lower 2 bits are the data flag DF and the command flag CF, and the upper 4 bits are the command holding bit.
In FIG. 11, AIB is an address input buffer,
MPX is an address multiplexer.

As described above, the command latched in the command latch CL is decoded by the command decoder DEC to set the command flag CF. If this processing is entrusted to the CPU 10, the CPU 10 has to start a bus cycle and constantly monitor the content of the command latch CL, which causes a waste of operation. Further, if the CPU 10 analyzes all the commands of the command latch CL according to the set state of the command flag CF controlled by the command decoder DEC, the operation instructed by the command may not be in time. For example, flash memory F
It is a read type command for reading data from MRY2. In order to deal with this, as shown in FIGS. 11 and 12, a state in which the command latch CL, the data latch DL, and the address latch AL are connected to the flash memory FMRY2 and the CPU 10, and the command latch C is used.
A bus switch BSW capable of selecting a state in which L, the data latch DL, and the address latch AL are connected to the flash memory FMRY2 and are not connected to the CPU 10,
The internal bus ABUS and DBUS are provided, and the bus switch BSW thereof is controlled by a signal obtained from the decoding result of the read system command by the command decoder DEC. When the bus switch BSW is opened, the flash memory FMRY2 is supplied from the outside of the microcomputer MCU3, in other words, the PROM writer 3
Direct read access is enabled from 0.

[7] Command specifications for information writing by PROM writer

FIG. 13 shows an example of specifications of commands that can be supplied from the PROM writer 30. The command shown in the figure is not particularly limited, but there are eight types, and the contents of the cycle in which the PROM writer 30 should be activated are shown corresponding to each command. The command code corresponds to the first cycle data shown in FIG. This code is shown by a hexadecimal number, and H added at the end of the code means that it is a hexadecimal number. The read command (Read) is a command for reading data from the flash memory FMRY2. RA in the second cycle of the command means a read address.
The read ID command (Read ID) is a command for reading the product identification code (ID) from the product identification code address (IA). Erase command (Erase)
Is a command to erase the data in the flash memory. At the time of erasing, in order to avoid over-erasing (a phenomenon in which Vth of the memory becomes negative when over-erasing is performed and normal reading cannot be performed), pre-writing for equalizing the write level before erasing is performed, An erasing procedure of erasing little by little while verifying is adopted. The erase verify command (E Verify) is a command for confirming the erased state. EA is a memory address for erase verification. EVD is erase verify output data. Automatic erase mode (AE
(rase) is a command for automatically performing erase and erase verify. After completion of automatic erase, status polling can confirm the end of automatic erase operation. The status polling flag SPF is assigned to the upper bit of the data latch DL in FIG. The write command (Program) is a command for instructing writing, and PA is a write address and P is a write address.
D is write data. The program verify command (P Verify) is a command for confirming whether the data written immediately before is correctly written,
PVD is program verify output data. The reset command (Reset) is a command for resetting the command when the command is mistaken.

The command specifications are not particularly limited, but the HN28F described in pages 868 to 881 of "Hitachi IC Memory Data Book 1" issued in September 1991.
It is compatible with the command specifications of a 101 series flash memory LSI (1M bit flash memory).

[8] On-board information writing operation

All instructions and procedures for writing information in the on-board state are controlled by the CPU 10 and its operation program, and information writing processing is controlled by setting / clearing each bit of the control register CREG by software. . When the rewriting program at this time is placed in the flash memory FMRY2, the rewriting program is transferred to the RAM in advance at the time of the information writing operation or the system reset, and the CPU 10 executes the program on the RAM. And rewrite information. An example of the rewriting processing procedure at this time will be described below in this item.

Writing of information to the flash memory is basically performed to the memory cell in the erased state.
When the flash memory is rewritten with the microcomputer installed in the system, the rewrite control program to be executed by the CPU 10 is the erasing program,
The rewrite control program may be configured to include a program for writing, and to execute the erasing processing routine first and then automatically execute the writing processing routine in accordance with the information writing instruction. Alternatively, erasing and writing may be divided and the operation may be instructed separately.

14 and 15 show detailed examples of the write control procedure. The control subject of the procedure shown in the figure is the CPU 10.

In the first step of writing data in byte units, the CPU 10 sets 1 in its built-in counter n (step S1). Next, the CPU 10 sets the data to be written in the flash memory FMRY2 in the data input latch DIL of FIG. 11 and sets the write address in the address latch AIL (step S2). The CPU 10 then controls the control register C
A write cycle is issued to REG to set program bit P (step 3). As a result, the control circuit FCONT performs writing by applying a high voltage to the control gate and drain of the memory cell designated by the address based on the data and address set in step S2. As the write processing time on the flash memory side, the CPU 10 waits for (x) μsec (step S4), and then clears the program bit P (step S5). Here, the time of (x) μsec is determined according to the characteristics of the memory cell, and is, for example, 10 μm.
The time is set to sec.

Thereafter, the CPU 10 issues a write cycle to the control register CREG to confirm the write state, and the program verify bit P
V is set (step 6). As a result, the control circuit F
The CONT uses the address set in step S2, applies a verify voltage to the word line to be selected by the address, and reads the data in the written memory cell. (Y) μse for reading
Wait c (step S7). Here, the verify voltage is set to a voltage level such as 7V which is higher than the power supply voltage Vcc such as 5V in order to ensure a sufficient write level. (Y) sec is determined by the rising characteristics of the verifying power supply, and is, for example, 2 μm.
It is set to sec or less. The CPU 10 confirms that the data read thereby matches the data used for writing (step S8). When the CPU 10 confirms the match by the verify, the program verify bit PV
Is cleared (step S9), whereby the writing of the 1-byte data is completed.

On the other hand, when the CPU 10 confirms the mismatch by the verify in step S8, it clears the program verify bit PV in step S10 and then determines whether the value of the counter n has reached the write retry upper limit number N or not. Perform (step S11). As a result,
When the write retry upper limit number N has been reached, the process ends as a write failure. When the write retry upper limit number N has not been reached, the CPU 10 increments the value of the counter n by 1 (step S1).
2) The process is repeated from step S3.

16 and 17 show a detailed example of the erase control procedure. The control subject of the procedure shown in the figure is C
It is PU10.

When erasing, the CPU 10 sets 1 in its built-in counter n (step S21). Next, the CPU 10 prewrites the memory cell in the erase target area (step S22). That is, data "0" is written in the memory cell of the erase target address. This pre-write control procedure is shown in FIG. 14 and FIG.
The write control procedure described in 1. can be applied. This pre-write process is performed in order to make the amount of charge in the floating gate before erasing uniform for all bits and make the erased state uniform.

Next, the CPU 10 issues a write cycle to the erase block designating register MBREG,
A memory block to be erased collectively is designated (step S2
3). That is, the erase block designation register MBREG
The memory block number to be erased is designated in 1 and MBREG2. After specifying the memory block to be erased,
The U10 issues a write cycle to the control register CREG to set the erase bit E (step 24). This causes the control circuit FCONT to
A high voltage is applied to the source line of the memory block designated in step S23 to erase the memory block at once. The CPU 10 waits, for example, (x) msec as the processing time for batch erasing on the flash memory side (step S25). Here, (x) msec is determined according to the characteristics of the memory cell transistor, and is, for example, 10 ms.
ec. This time (x) msec is shorter than the time required to complete the erase operation once. Then, the erase bit E is cleared (step S26).

Thereafter, in order to confirm the erased state, the CPU 10 first sets the start address of the batch erase target memory block as the address to be verified internally (step S27), and then performs a dummy write to the verify address (step S27). S28). That is, the memory write cycle is issued to the address to be verified. As a result, the memory address to be verified is held in the address latch AIL. Then CPU
10 issues a write cycle to the control register CREG to set the erase verify bit EV (step 29). As a result, the control circuit FC
The ONT uses the address set in step S28 to apply an erase verify voltage to the word line to be selected by the address, and reads the data in the erased memory cell. (Y) μsec to read
Wait (step S30). Here, the erase verify voltage is, for example, 5 V in order to guarantee a sufficient erase level.
The voltage level is 3.5V, which is lower than the power supply voltage Vcc. The (y) μsec is determined by such a rising characteristic of the verifying power supply, and is set to 2 μsec or less, for example. CPU10
Verifies whether the data read thereby matches the data in the erase completed state (step S31).
When the CPU 10 confirms the match by verifying,
Erase verify bit EV is cleared (step S
32) Next, it is judged whether or not the verify address of this time is the final address of the erased memory block (step S33), and if it is the final address, a series of erasing operations are ended. If it is determined that the final address has not been reached, the verify address is incremented by 1 (step S34), and the processing from step S28 is repeated.

On the other hand, when the CPU 10 confirms the disagreement by the verification in step S31, the CPU 10 proceeds to step S35.
After clearing the erase verify bit EV at, it is determined whether the value of the counter n has reached the upper limit number of times N of erasure (step S36). As a result, if the erasure upper limit number N has been reached gradually, the process ends as an erasing failure. When the erasure upper limit number N has not been reached, the CPU 10 increments the value of the counter n by 1 (step S37), and then the step S2.
The process is repeated from 4. In practice, in order to prevent over-erase in which the threshold voltage of the memory cell becomes a negative value due to over-erasing, verify is performed every time and gradually a short time such as 10 msec. Erasing is repeated.

[0081]

[9] Information writing operation by command method (command compatible)

When the information writing mode by the PROM writer is set in the microcomputer MCU3 via the mode signals MD0 to MD2, the flash memory FMRY
The PROM writer 30 is used for writing information 2 in a method called a command method. Here, the command method means that an instruction such as information writing to the flash memory is given by a command from an external device such as the PROM writer 30. The processing according to the command is controlled by the CPU 10. The control program for that purpose is included in the flash memory FMRY2 and is stored in the PROM.
The program is transferred to the RAM in response to the setting of the information writing mode by the writer 30, and the CPU 10 executes the control program transferred to the RAM. This operation program may be partially shared with the program for controlling the writing of information in the built-in flash memory in the on-board state, or may be completely separate. The command specifications are as described above with reference to FIG. 13, and the operation will be described below for each command.

(1) Write command The PROM writer 30 is asynchronous with the CPU 10, and
Write commands, data, and addresses according to the command specifications of. The CPU 10 first sets the command flag CF.
= 1 (command already input) or data flag DF = 1 (command input and data input), read command, and after command recognition data flag DF = 1 The operation to go to read data and address is performed. PROM writer 3
The command supplied from 0 is the command flag CF = 0.
And the command latch CL according to the data flag DF = 0
Latched on. The data to be written in the memory cell is the command flag CF = 1 and the data flag DF = 0.
Is latched by the data latch DL. CPU10
When recognizing that the read command is a "write command", the address and data are read from the address latch AL and the data latch DL in accordance with the operation program, and the address input data AIL and the data input latch DIL in the flash memory FMRY2 are read. Transfer address and data. Then, the CPU 10 actually writes in the memory cell of the flash memory FMRY2 by setting the write bit (P bit) of the control register CREG. The actual write processing procedure for the memory cell is substantially the same as the content described with reference to FIG.
After writing, clear P bit and clear CF and DF to 0
Return to. State of flags CF and DF and C during write operation
A summary of the operation of the PU 10 is shown in FIG.

(2) Write Verify Command In writing, the write verify mode is always executed at the end of the operation. The write verify is an operation for confirming whether the data written immediately before is written. In the case of this command, the operation up to the analysis of the command is performed in the same manner as the write command. When the CPU 10 recognizes that the command is the write verify command, the CPU 10 performs control according to the following procedure. First, the PV bit (program verify bit) of the control register CREG is set to "1". Flash memory F at this time
Since the address at the time of the immediately preceding write is latched in the address latch AIL in MRY2, the verify voltage (for example, 7v) is applied to the word line selected by this address. Next, the CPU 10 reads the flash memory FMRY2. In this case also, since the latched address is used as the address,
Eventually, the reading is performed in the state where the verify voltage is applied as the gate voltage to the memory cell in which the writing is performed first. The CPU 10 writes the read data in the data latch DL of the port PORT, and PV
The operation ends by clearing the bit. PR
The OM writer 30 performs verification by reading the value of the data latch DL. The state of the flags and the operation of the CPU 10 at the time of write verify are shown together in FIG.

(3) Erase Command According to the microcomputer MCU3 of the present embodiment, the internal flash memory FMRY2 is erased by the 1M flash memory (HN) as the flash memory single LSI.
28F101), the block erase is not supported and only the matte batch erase is performed. FIG.
As is clear from the command specifications of
When data is written twice, erasing starts. In the case of erasing, the operation up to command analysis is the same as in writing. The erasing is started by setting the erasing block designating register MBREG to the all bit selection state and then setting the E bit (erase bit) of the control register CREG to "1". By setting the E bit, a high voltage is applied to the source line of the memory mat to erase it. After the E bit is set to "1" for a certain period of time, it is cleared and the erasing is completed. The erase control procedure for the memory cell is substantially the same as the control content described in FIG. 2A.

(4) Erase Verify The verify executed after erasing the command is similar to the write verify. After the command analysis, the CPU 10 reads the address to be verified from the port address latch AL and writes it in the flash memory FMRY2.
Next, the CPU 10 makes the EV of the control register CREG
By setting the bit, a verify voltage (for example, 3.5v) is applied to the word line selected by the previously latched address. In this state, the CPU 10 reads the flash memory FMRY2 and writes the read data in the data latch DL of the port. Then E
The V bit is cleared and the operation ends.

(5) Automatic erasing command After recognizing the automatic erasing command, the CPU 10 itself performs all the erasing flows shown in FIGS. 16 and 17. In automatic erasing, the flash memory FMRY2 is designed to output a status polling signal at the start of erasing and invert the signal at the end of erasing. Since the status polling output is I / O7, the 7th bit of the data latch DL is used as a bit for storing the status polling signal. C
The PU 10 clears the 7th bit of the data latch DL at the start of erasing and sets it at the end of erasing.

(6) Read Command When a read command (read command) is issued, the flash memory FMRY2 needs to be ready to be read by the PROM writer 30. In the method described above, since the CPU 10 analyzes the command, it takes a long time from when the command is input to when the command is ready to be read, and the specification of the 1M flash memory cannot be met. Therefore, in the read mode, the CPU 10 is disconnected by the bus switch BSW so that the built-in flash memory FMRY2 can be directly accessed from the outside. The CPU 10 requests the bus right release BR
Although an EQ (bus request) signal can be input from the outside, it takes time until the CPU 10 releases the bus, so the bus switch BSW physically disconnects the bus. Since it takes time in all cases via the CPU 10, when the decoder DEC recognizes that the command is a read system command, it immediately disconnects the bus. At this time, in order to prevent the CPU 10 from recognizing that a command has been input, the command flag CF = 0 is kept in the case of a read command, and the command flag CF = 0 to the command flag CF = only in the case of other commands. The flag is changed to 1.

(7) Reset command A reset command is prepared in case the command setup is mistaken. As is clear from the command specifications of FIG. 13, the specification is such that the reset is completed by writing this reset command twice. In the microcomputer MCU3 of this embodiment, if a command is input again after the first input of some command, the command is input to the data latch DL.
The reset command written first may be recognized as the data FFH. However, in the flash memory, the erased state in which electrons are extracted from the floating gate is "1".
Therefore, even if the write command is input first, FFH is equivalent to not writing anything and there is no problem. Then, when the reset command written the second time is decoded by the command decoder DEC,
The read state is left as it is in the read mode, and the operation ends. State of flag at reset and CPU
The operation of 10 is collectively shown in FIGS. 20 and 21.

[10] Operation of PROM writer 30 when writing information by command method

22 and 23 show operation flowcharts of the PROM writer 30 at the time of writing information. First, a high voltage such as 12 V required for writing is output to the terminal Vpp (step S40), the built-in address counter is initialized to 0 (step S41), and the counter n is set to 0 (step S42). Then, the counter n is incremented by 1 (step S43), and then the write cycle of the program command is activated to write the write command (40H) in the command latch (step S44). Then, the write data (PD) and the write address (PA) are written in the data latch DL and the address latch AL (step S45). Then, for example, wait for 25 μsec (step S46). During this time, the CPU 10 of the microcomputer interprets the command and writes the data in the flash memory FMRY2. Then, this time, the write cycle of the write verify command is activated (step S47), and waits, for example, 6 μsec (step S48). During this time, the CPU 10 of the microcomputer MCU3 interprets the command and reads the data of the write address into the data latch DL. PROM writer 3
For 0, the read data is taken in and it is judged whether or not the data could be written normally (step S49). When it is determined to be normal, it is determined whether it is the final write address (step S
50) If it is not the last, the write address is incremented (step S51), then the process returns to step S42, and after writing to the final address, a voltage Vcc such as 5V is applied to the terminal Vpp (step S5).
2), writing is completed. If it is determined in step S49 that the writing is abnormal, the value of the counter n is 2 at the maximum.
The process returns to step S43 again until 0 is reached, and the writing is repeated. If the writing abnormality is still not solved even after repeating 20 times, the processing is terminated because the address is a defective bit.

24 and 25, PR for erasing
An operation flowchart of the OM writer 30 is shown. First, data having a logical value of 0 is written in all bits to be erased in the flash memory. The writing process complies with FIG. 22 and FIG.
Next, the start address of the erase area is set in the address counter (step S61), and the counter n is set to 0 (step S62). Next, the counter n is incremented by 1 (step S63), and then the erase command write cycle is activated to write the erase command (20H) to the command latch (step S64). Then, for example, wait 10 msec (step S65). During this time, the CPU 10 of the microcomputer MCU3 interprets the command and erases the flash memory FMRY2. Then, this time, the write cycle of the erase verify command is activated (step S66) and waits, for example, 6 μsec (step S67). During this period, the microcomputer MCU
The CPU 10 of No. 3 interprets the command, reads the data of the erase verify address (EA), and outputs the data latch D.
Transfer to L. The PROM writer 30 takes in the read data and determines whether the data can be erased normally (step S68). If it is determined to be normal, it is determined whether it is the final erase address (step S69), and if it is not the last one, the erase verify address is incremented (step S69).
70), and thereafter, the process returns to step S66, erase verification is performed up to the final address, and the process ends. If the erase abnormality is determined in step S68, the process returns to step S63 again to repeat the erase until the value of the counter n reaches 3000 at the maximum, and if the erase abnormality is still not solved even after repeating 3000 times, the address is deleted. Is a defective bit and the process is terminated.

[11] Operation of CPU when writing information by command system

FIG. 26 shows a main flowchart of the processing for the various commands by the CPU 10.
The CPU 10 samples the command flag CF and the data flag DF, and when detecting the set state thereof, reads the upper 4 bits of the command latch CL and analyzes the command. When it is A0H, erase verify (Erase Verify), and when it is C0H, write verify (Program Veri).
fy), write when 40H (Program), 2
The processing routine branches to each processing of erasing (Erase) when 0H and automatic erasing (Auto Erase) when 30H. The description of the other commands described in FIG. 13 will be omitted.

In the erase (Erase) processing routine,
As shown in FIG. 27, after controlling the sequence necessary for erasing the flash memory, the command flag CF is cleared and the process ends. In the erase verify (erase verify) processing routine shown in FIG.
The erase verify address is fetched from the address latch AL, the erase verify mode is set in the control register CREG, the data at the address is read and transferred to the data latch DL. Auto Erase (Auto Er
In the processing routine of (ase), as shown in FIG. 28, after performing pre-write execution control for all addresses of the built-in flash memory FMRY2, erase control is performed, and then erase verify is performed. Erase and erase verify control are performed until all addresses are erased.
If the erase state is repeatedly judged by the erase state and the upper limit of the erase time is exceeded, the process ends with the presence of a defective bit. In the write (Program) processing routine, as shown in FIG. 29, when the set state of the data flag DF is determined, the write address is fetched from the address latch AL and the write data is fetched from the data latch DL, and the flash memory is fetched. FMRY2
The data flag DF is cleared, and the process ends. Write verify (Program
In the (Verify) processing routine, as shown in FIG. 29, the write verify mode is set in the control register CREG, the data is read from the immediately preceding write address, this is transferred to the data latch DL, and the command flag CF is cleared. Then, the process ends.

[12] Compatibility of a PROM writer with a single flash memory LSI

Specifications for writing information in the built-in flash memory FMRY2 by the command method using the PROM writer 30, and the single flash memory LSI (H
The present inventor has confirmed the compatibility with N28F101) specifications for writing information using the PROM writer 30. According to this, in order to make the information writing by the PROM writer 30 the same specification as the 1M flash memory single LSI (HN28F1013),
It is necessary to match various timings with the 1M flash memory. Therefore, we actually created a control program and examined whether the timing could be adjusted. The result of this examination is shown in FIG. From these results, it was confirmed that they were compatible at an operating frequency of 16 MHz, for example.

According to the above embodiment, the following operational effects can be obtained.

(1) Since the rewriting sequence corresponding to the command asynchronously given from the PROM writer 30 is realized by the built-in circuit of the microcomputer, the data information is given to the PROM writer 30 before giving the data information and the address information. Write the command to the command latch in the same way as in
By connecting to the M writer 30 via a socket adapter, information can be written in the flash memory built in the microcomputer.

(2) By causing the built-in CPU 10 to control the rewriting sequence instructed by the command, a dedicated circuit for the control can be eliminated or reduced, and the chip area of the microcomputer can be reduced. Further, the control sequence for rewriting is the CPU1
Since 0 can be changed by software to be executed, it is possible to easily set the conditions such as the write time according to the characteristics of the storage element forming the flash memory.

(3) The PROM writer 30 used for general purpose applies at least a high voltage for rewriting to the non-volatile memory element, and writes the address and data for rewriting according to the write signal or the like to the target semiconductor including the flash memory. It is supplied to a device (LSI). Such a PROM writer 30 supplies commands, data, and addresses asynchronously with the microcomputer built-in CPU 10. At this time, a command flag CF indicating that a command has been written to the command latch CL, and a data latch that is externally writable in place of the command latch CL when the command flag CF indicates a command latch state. By including the DL, it is possible to prevent a command and data information written from the PROM writer 30 in mutually different cycles from colliding on the latch means.

(4) The CPU 10 sends the command flag CF
The command of the command latch CL is read based on the command latch state of
Command decoder DEC that decodes the latch contents of L and sets the command flag CF to the command latch state
By providing the, it is possible to speed up the setting process for the command flag. If the control of the command flag is also entrusted to the CPU 11, the CPU 11
Must start the bus cycle and constantly monitor the content of the command latch CL, which causes waste in operation and delays flag processing.

(5) The command decoder DEC is provided with the bus switch BSW for disconnecting the CPU 11 from the flash memory according to the result of decoding of the read command, so that the CPU 10 analyzes all the commands latched in the command latch. It is possible to easily deal with a read-type command that is not in time for the operation instructed by. This means that PROM is
This makes it possible for the writer 30 to achieve compatibility with the writing process for the single flash memory LSI.

(6) The procedure control program for rewriting the flash memory to be executed by the CPU 10 is stored in the flash memory, and the program is stored in the RAM in response to the setting of the rewriting operation mode by the PROM writer 30. By transferring and causing the CPU 10 to execute the program transferred to the RAM,
The rewriting program can be easily modified.

(7) Considering that the amount of information to be stored in the flash memory differs depending on the type of the information, such as a program, a data table, control data, etc., depending on the application, batch erasing in the flash memory By providing a plurality of memory blocks with mutually different storage capacities as a possible unit, the memory blocks can be grouped together when the information stored in the internal flash memory is partially or partially rewritten after system installation. It is possible to improve the rewriting efficiency by eliminating the waste of the writing operation after erasing.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Yes.

For example, the peripheral circuit built in the microcomputer is not limited to the above-mentioned embodiment, but can be changed as appropriate. The memory cell transistor of the flash memory is not limited to the stacked gate structure MOS transistor of the above embodiment, and it is also possible to use a FLOTOX type memory cell transistor using the tunnel phenomenon for the write operation. In addition, the unit of collective erasure can be a memory block in which the source lines are shared, or a memory block in which word lines can be shared during erasure.
Which one is selected depends on the polarity of the erase voltage or the number of memory cells connected to a single word line and a single data line when the storage capacity of the batch erase unit is to be minimized. It can be determined in consideration of circumstances such as which one is smaller than the number of memory cells connected to the line. The size of the memory block is not limited to the fixed size as in the above embodiment. For example, the size can be made variable according to the setting of the control register or the instruction of the mode signal. For example, when a batch erase voltage is applied with the word line as the minimum unit, the operation of the driver for driving the word line with the erase voltage may be selected according to the setting of the control register or the instruction of the mode signal. Further, as a division mode of the memory block, the whole is divided into a plurality of large blocks, and each of the large blocks is divided into a plurality of small blocks so that they can be collectively erased in a large block unit or a small block unit. It is also possible to do so. Further, in the method of rewriting the flash memory under the control of the CPU, it is also possible to employ software for self-tuning the rewriting conditions and the like. In addition, in a memory cell transistor of a flash memory, its source and drain may be understood as a relative one determined by an applied voltage.

The present invention can be widely applied to a data processing device provided with a central processing unit and an electrically rewritable nonvolatile flash memory on at least a single semiconductor chip.

[0109]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

By implementing the rewriting sequence according to the command asynchronously given from the external device by the built-in circuit, before the data information and the address information are given to the external device, the command is transmitted in the same manner as the data information is given. It suffices to provide it to the processing device, and by connecting it to an external device such as a PROM writer used for general purpose through a socket adapter, it is possible to easily write information to the flash memory built in the data processing device. There is.

By controlling the rewriting sequence instructed by the command by the built-in central processing unit, a dedicated circuit for the control is unnecessary or eliminated,
The chip area of the data processing device is reduced. Furthermore, the control sequence for rewriting can be changed by software executed by the central processing unit, which has the effect of easily setting the conditions such as the write time according to the characteristics of the storage elements forming the flash memory. is there.

Flag means for indicating that a command has been written in the command latch means, and data latch means that is externally writable in place of the command latch means when the flag means indicates the command latch state. By including the above, it is possible to prevent the command and the data information, which are written in different cycles from an external device such as a PROM writer, from colliding on the latch means.

By adopting a command decoder which decodes the latch contents of the command latch means and decodes the predetermined command to set the flag means to the command latch state, the processing for the flag means is speeded up. be able to.

By providing the gate means for disconnecting the central processing unit from the flash memory according to the decoding result of the read command by the command decoder, the central processing unit may have analyzed all the commands latched in the command latch means. It is possible to easily deal with a read command in which the timing of the operation instructed by is not in time. This makes it possible to realize the compatibility of the flash memory with the built-in data processing device with the writing process to the single flash memory LSI for an external device such as a PROM writer.

Considering that the amount of information to be stored in the flash memory differs depending on the type of the information, such as a program, a data table, control data, etc., depending on the application, a batch erasable unit in the flash memory. As a result, by providing a plurality of memory blocks having mutually different storage capacities, writing after erasing all the memory blocks collectively with the partial or partial rewriting of the retained information in the internal flash memory after the system is mounted. Rewriting efficiency can be improved by eliminating waste of operation.

[Brief description of drawings]

FIG. 1 is a functional block diagram when a PROM writer rewrites a built-in flash memory in a microcomputer according to a first embodiment having a built-in flash memory.

FIG. 2 is a functional block diagram when rewriting processing of the built-in flash memory by a PROM writer in the microcomputer according to the second embodiment having the built-in flash memory.

FIG. 3 is a timing chart of an example of command writing by a PROM writer.

FIG. 4 is a timing chart of an example of an information write cycle of a flash memory under CPU control.

5 is an explanatory diagram showing a difference in effect between the first embodiment of FIG. 1 and the second embodiment of FIG.

FIG. 6 is a block diagram of a more detailed embodiment of a microcomputer corresponding to the microcomputer of FIG.

FIG. 7 is a plan view showing the microcomputer of FIG. 6 under a packaging tool.

8 is an overall block diagram of a flash memory incorporated in the microcomputer of FIG.

FIG. 9 is an explanatory diagram showing an example of a division mode of a memory block.

FIG. 10 is an explanatory diagram of an example of a control register and an erase block designation register.

11 is a block diagram showing details of hardware for supporting a PROM writer rewriting mode by a command method in the microcomputer of FIG. 6;

FIG. 12 is an explanatory diagram showing command flags, data flags, and bus switch control formats.

FIG. 13 is an explanatory diagram of an example of commands that can be supplied from a PROM writer.

FIG. 14 is a detailed example flowchart showing the first half of the write control procedure in the on-board state.

FIG. 15 is a detailed example flowchart showing the latter half of the write control procedure in the on-board state.

FIG. 16 is a detailed example flowchart showing the first half of the erase control procedure in the on-board state.

FIG. 17 is a detailed example flowchart showing the latter half of the erase control procedure in the on-board state.

FIG. 18 is an explanatory diagram summarizing the states of flags CF and DF and the operation of the CPU during the write operation by the PROM writer.

FIG. 19 is an explanatory diagram summarizing the states of flags and the operation of the CPU at the time of write verification by the PROM writer.

FIG. 20 is a first explanatory diagram summarizing the states of flags at the time of resetting by the PROM writer and the operation of the CPU.

FIG. 21 is a second explanatory diagram summarizing the states of flags at the time of resetting by the PROM writer and the operation of the CPU.

[Fig. 22] P for writing information by the command method
6 is an example flowchart showing the first half of the operation of the ROM writer.

[FIG. 23] P for writing information by a command method
7 is an example flowchart showing the latter half of the operation of the ROM writer.

FIG. 24 is a PROM when erasing by the command method.
An example flow chart showing the first half of the operation of the writer is shown.

FIG. 25 is a PROM when erasing by the command method.
An example flow chart showing the latter half of the operation of the writer is shown.

FIG. 26 is a main flowchart of the processing of the CPU with respect to the command given from the PROM writer.

FIG. 27 is a processing routine of erase (Erase) and erase verify (Erase Verif) shown in FIG. 26;
It is a flow chart which shows a processing routine of y).

FIG. 28 is an automatic erasure document (Auto E shown in FIG.
(rase) processing routine.

FIG. 29 is a diagram showing the writing (Program) shown in FIG. 26;
Processing routine and write verify (Program
It is a flowchart which shows the processing routine of (Verify).

FIG. 30 is an explanatory diagram showing a result of examining a writing specification by a PROM writer.

FIG. 31 is a diagram illustrating the principle of a flash memory.

FIG. 32 is an explanatory diagram of a configuration principle for a memory cell array of a flash memory.

FIG. 33 is an explanatory diagram showing an example of voltage conditions for an erase operation and a write operation for a flash memory.

FIG. 34 is a circuit block diagram of an example of a flash memory in which the memory capacities of batch-erasable memory blocks are different.

[Explanation of symbols]

MCU1 microcomputer MCU2 microcomputer MCU3 microcomputer 10 CPU FMRY2 flash memory 21 Command Latch Means 22 Command analysis means 23 Sequence control means 30 PROM writer CREG control register MBREG erase block specification register SMB0 to SMB7 Small memory block LMB0 to LMB6 Large memory block CL command register CF command flag DF data flag DL data register AL address register DEC command decoder BSW bus switch Q1 to Q4 memory cell transistors SL1, SL2 source line DL1, DL2 data line WL1, WL2 word line

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hirofumi Mukai             5-20-1 Kamimizuhonmachi, Kodaira-shi, Tokyo Stock             Ceremony company Hitachi Ltd. Musashi factory (72) Inventor Eiichi Ishikawa             5-20-1 Kamimizuhonmachi, Kodaira-shi, Tokyo Stock             Ceremony company Hitachi Ltd. Musashi factory F-term (reference) 5B062 CC03 EE09

Claims (5)

[Claims] 1. A microcomputer having a first operation mode in which a central processing unit and an electrically rewritable flash memory are formed on one semiconductor substrate and which operates in accordance with a command input from an external device. And a bus connected to the central processing unit, the flash memory and the external terminal, and a read command for reading information stored in the flash memory from the external device in the first operation mode. A microcomputer characterized by disconnecting the central processing unit from the bus when input to the microcomputer. 2. The microcomputer according to claim 1, further comprising a command latch unit for writing a command input from the external device, a command analysis unit for analyzing the command latched in the command latch unit, and an analysis unit. The microcomputer further comprising: a control unit that controls a procedure for rewriting the flash memory according to the contents. 3. The microcomputer according to claim 2, wherein the analysis unit and the control unit are the central processing unit. 4. The flash memory according to claim 2, further comprising flag means indicating that a command has been written in the command latch means, wherein a command input from the external device writes information in the flash memory. If it is
Write information indicating that a command has been written to the flag means, and do not write information indicating that a command has been written to the flag means when the command input from the external device is the read command. Microcomputer characterized by. 5. A microcomputer characterized by disconnecting a central processing unit from a bus when reading information in a built-in flash memory from an external device.