User`s manual

8-1
Chapter 8. Maintenance and check
8-1 Self-diagnosis function
By the self-diagnostic function, the system is running while checking if its own hardware is normal or not.
As a result of self-diagnosis, if abnormality is detected, the stop output is turned OFF (opened), and the
fault lamp lights up to stop operation.
Self-diagnosis is executed in every scan, and when recovered to normal state, the stop output is
automatically turned ON (closed), and the operation is resumed. (By the infinite loop of user program or
the like, when the watchdog timer is actuated, the operation is stopped by the program mode, and the
stop output is opened.)
[1] Abnormality not detected by self-diagnostic function
1. Abnormality directly affecting the self-diagnostic function itself of the control module (such as
hardware abnormality of control module)
2. Abnormality in the outer side circuit module of input and output module (abnormality not affecting
the I/O bus port)
Examples:
- When the load cannot be driven due to abnormality of output transistor of output module.
- When input signal cannot be taken in due to abnormality of photo coupler of input circuit of input
module.
3. Communication abnormality in data link
Communication abnormality can be confirmed by the LED of option module or communication
flag.
For details, see "user's manual" of option module.