Omron CJ1M-CPU series User Manual

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Fail-safe Circuits Section 5-1

5-1 Fail-safe Circuits

Be sure to set up safety circuits outside of the PLC to prevent dangerous con-

ditions in the event of errors in the PLC or external power supply.

Supply Power to the PLC

before Outputs

If the PLC’s power supply is turned on after the controlled system’s power

supply, outputs in Units such as DC Output Units may malfunction momen-

tarily. To prevent any malfunction, add an external circuit that prevents the

power supply to the controlled system from going on before the power supply

to the PLC itself.

Managing PLC Errors When any of the following errors occurs, PLC operation will stop and all out-

puts from Output Units will be turned OFF.

• Operation of the Power Supply Unit’s overcurrent protection circuit

• A CPU error (watchdog timer error) or CPU on standby

• A fatal error* (memory error, I/O bus error, duplicate number error, too

many I/O points error, program error, cycle time too long error, or

FALS(007) error)

Be sure to add any circuits necessary outside of the PLC to ensure the safety

of the system in the event of an error that stops PLC operation.

Note *When a fatal error occurs, all outputs from Output Units will be turned OFF

even if the IOM Hold Bit has been turned ON to protect the contents of I/O

memory. (When the IOM Hold Bit is ON, the outputs will retain their previous

status after the PLC has been switched from RUN/MONITOR mode to PRO-

GRAM mode.)

Managing Output

Malfunctions

It is possible for an output to remain ON due to a malfunction in the internal

circuitry of the Output Unit, such as a relay or transistor malfunction. Be sure

to add any circuits necessary outside of the PLC to ensure the safety of the

system in the event that an output fails to go OFF.

Emergency Stop Circuit The following emergency stop circuit controls the power supply to the con-

trolled system so that power is supplied to the controlled system only when

the PLC is operating and the RUN output is ON.

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General

Series	CJ1M
Program Memory	Flash Memory
Power Supply Voltage	24V DC
Operating Temperature	0 to 55°C
Type	Programmable Controller
CPU Type	CPU11, CPU12, CPU13, CPU21, CPU22, CPU23
Data Memory	SRAM
Data Memory Capacity	32K words (CJ1M-CPU11/12/13), 64K words (CJ1M-CPU21/22/23)
Instruction Execution Time (Basic Instructions)	0.1 μs (LD instruction)
Instruction Set	Basic instructions, advanced instructions
Programming Language	Ladder Diagram, Structured Text, Function Block Diagram
Communication Ports	RS-232C
Expansion Slots	Up to 3
Mounting	DIN rail mounting
Storage Temperature	-25 to 70°C
Dimensions	90 x 90 x 70 mm
Weight	Approx. 200g (0.44 lb)
Number of Instructions	Over 400 instructions