Chapter 13 Troubleshooting

(b)Will not operate (will not run)

Even if the PLC operation conditions are met, the CPU does not operate (the RUN LED does not turn on) and remains stopped. However, the peripheral units go on-line.

Caution

If the CPU is WRITE-occupied, the CPU will not run even if the RUN switch is switched from “STOP” to “RUN.” The CPU starts running by pressing the GRS key after peripheral units are connected.

Self-diagnostic error code

YES

 

27

 

31

 

33

 

 

 

Serious memory error

NO

Self-diagnostic error code

YES

 

23

 

34

 

44

 

45

 

 

 

 

 

 

 

Serious user program error

Check the memory

Perform CPU initialization Set memory parameters Reset the power Replace CPU if above steps does not remedy the problem

NO

Check I/O assignments

Check the assignment table at peripheral devices

Can I/O assignment be corrected?

Malfunction due to noise

Check the user program

Check programs using peripheral devices

Error special internal output monitor

Verify scan time

Correct program

13-8

Page 283
Image 283
Hitachi NJI-350B manual 13-8