JPS6225335A - Sequencer - Google Patents

Abstract

PURPOSE:To prevent an EEPROM from being rewritten owing to the runaway of a CPU by allowing a runaway detecting means to detect access to an external ROM for sequence program storage not being attained at a constant period by using the EEPROM. CONSTITUTION:A write control circuit 7 triggers periodically a retriggerable monostable multivibrator 9 which detects a runaway with an output signal from a decoder 8 by the addressing of a CPU 1 and also inputs the Q output of the monostable multivibrator 9 and a write signal WT from the CPU 1 to a OR gate 10 to place the EEPROM 6 in a write enable state. When access from the CPU 1 is cased owing to the runaway while the write signal WT is generated and then the Q output of the monostable multivibrator 9 is inverted a specific time later, a write enable WE is at L from the generation of the write signal WT to the inversion. The EEPROM 6 is not rewritten when this L period is within the time required for the writing of the EEPROM 6.

Description

[Detailed description of the invention] [Technical field] The present invention relates to a sequencer.

[Background technology] Generally speaking, the sequence program that operates a sequencer is usually stored in a memory consisting of RAM built into the sequencer itself, but with RAM, there is a risk that the written contents may change due to noise. Also, since it is a volatile memory element, battery backup is required, and when the line changes, it is difficult to change the program. Therefore, EPRO is used instead of RAM.
The method of driving with M is often used. But EPROM
Normally, sequencers do not have the high voltage needed to write programs to them, so they cannot be written directly. Therefore, you should either transfer the program to a cassette tape or use an EEPROM (
EPRO
The contents (from the cassette tape, E, or EPROM) had to be loaded into a ROM writer with a voltage that would allow writing to the M, and then written to the EPROM.

However, since cassette tapes are time-consuming, EEPR
OM is particularly utilized. Here, although EEPROM is non-volatile and can be rewritten with 5 volts, it has not been used in place of EPROM.

In other words, since writing is possible with the 5-volt voltage used in the sequencer, the write signal (W T
) is output from the control calculation CPU, and the sequence program is broken. This is because there was a fear that he would be

[Object of the Invention] The present invention has been made in view of the above-mentioned problems, and its purpose is to protect the EEF ROM when the CPU runs out of control.
! : To provide a sequencer which prevents the written sequence program from being destroyed and eliminates the troublesome work of saving the program by using an EEPROM which can be written by the sequencer's built-in power supply.

[Disclosure of the Invention] The present invention provides a sequencer that is composed of a CPU for control calculations, a program for control calculations of the CPU, a memory for processing, and a peripheral device, and is capable of operating a sequence program on an externally connected ROM. The ROM for storing the sequence program is an EEPROM that can be written using the power supply voltage built into the sequencer, and is accessed by the CPU at a constant cycle, and the output of the runaway detection means is inverted if the access is not performed for a predetermined period of time or more. and the write signal output from the CPU, the above EEPRO
The present invention is characterized in that it includes a write control circuit that enables M, and the predetermined time is set to be less than or equal to the time required to write EEPRO,M.

The present invention will be explained below with reference to Examples.

(几Figure 1 shows an embodiment. A CPU 1 for arithmetic processing is connected to a ROM 4 in which an operating program for control calculations is written via a data bus 2, an address bus 3, and a control bus.
and a processing RAM 5, and an upstream EEPROM 6 is connected to a socket provided externally. Is EEPROM6 5V used for sequencer? +! The written program is read out by the read signal RD from the CPUI, and when the write signal WT is input to the write enable terminal WE, the address accessed via the address bus 3 is written.
The data sent from data bus 2 is written.

The write control circuit 7 is intended to prevent the sequence program in the EEPROMG from being accidentally rewritten and destroyed when the CPU i goes out of control.During normal operation, it is periodically addressed by the CPU and is read from the defogger 8. The runaway detecting means periodically trigs the one-shot multi-vibrator 9 based on the output signal of the one-shot multi-pipe rake 9, and outputs the Q output of the one-shot multi-pipe rake 9 and the write signal WT from the CPU to the OR date 10. EEPROM when input and both are “L”
6 is loaded and enabled. Here, the one-shot multivibrator 9 inverts the Q output after the last tri-vibrator by means of an inverter circuit consisting of a resistor R and a capacitor C.

Normally, the one-shot multivibrator 9 is given a signal before the Q output is inverted, and the Q output remains as "I,". Therefore the CPU
When the write signal WT is output from 1 to 10
The output becomes L', the EEPROM 6 is set to the write state, and the contents are rewritten.

Next, CPU1 goes out of control, and in the worst case, Figure 2 (,
), the write signal WT is generated from the CPU 1, and there is no access from the CPU 1 due to runaway, and the Q output of the one-shot multivibrator 9 is inverted after a predetermined time as shown in FIG. 2(b). Therefore, the write enable terminal WE becomes "L'' from the generation of the write signal WT until the Q output is inverted. Here, if this "L" period tw is within the time required for writing into the EEPROM 6, the contents of the EEPROM 6 cannot be rewritten and the previous sequence program is saved. In other words, in this embodiment, the time constant circuit is set so that the predetermined time from receiving the final trigger of the one-shot multivibrator 9 to inverting the Q output does not exceed the time required for this writing. , it is possible to save the sequence program at the time of the above-mentioned runaway.

[Effects of the Invention 1] The present invention provides a sequencer that is composed of a CPU for control calculations, a program for control calculations of the CPU, a memory for processing, and a peripheral device, and is capable of operating a sequence program using an externally connected ROM. The ROM for storing the sequence program is an EEPROM that can be written using the power supply voltage built into the sequencer, and is accessed by the CPU at a constant cycle, and the output of the runaway detection means is inverted if the access is not performed for a predetermined period of time or more. and the write signal output from CP and 11U, and the above EE is output.
It is equipped with a write control circuit that enables the PROM, and the predetermined time is set to less than the time required for writing to the EEPROM, so even if the CPU runs out of control, E
Since the contents of M are not rewritten, it is possible to use an EEPROM that can be rewritten using the power supply voltage built into the sequencer, and as a result, the writing operation can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention. Figure n2 is a time chart for explaining the operation of the same as above, 1 is the CPU, 4 is the R
OM, 5 is a RAM, 6 is an EEPROM, 7 is a write control circuit, 8 is a difugu, and 5] is a one-shot multivibrator. Agent Patent Attorney Ishi 1) Infringement 7 Proceedings r Sanno 8 (spontaneous) October 26, 1985 J'l - Director General of the Agency 1960 Patent Application No. 164366 2 Name of the invention Siegensa 3, Urasa Relationship to the matter Patent applicant address 1048 Kadoma, Kadoma City, Osaka Name <58
3) Matsushita Electric Works Co., Ltd. Representative: Sadao Fujii 1 Agent postal code: 530 Address: 1-12-17-17 Umeda, Kita-ku, Osaka 5 Weight of amendment order Voluntary issue: 6 Number of inventions to be increased by Urasa: None: 7 , Subject of amendment Description 8 Contents of amendment

Claims (1)

[Claims] (1) Consists of a CPU for control calculations, a program for CPU control calculations, a memory for processing, and peripheral devices,
In a sequencer that can operate a sequence program using an externally connected ROM, the ROM used to store the sequence program uses an EEPROM that can be written to using the power supply voltage built into the sequencer, and is accessed by the CPU at regular intervals. The above-mentioned EEPROM is activated when the output of the runaway detection means, which inverts the output when the output is lost for a predetermined period of time, coincides with the write signal output from the CPU.
1. A sequencer comprising a write control circuit for enabling said sequencer, said predetermined time being less than or equal to the time required for writing into an EEPROM.