Self-Diagnosis

Scan Watch Dog Timer

• Watch Dog Timer is used to detect the operation delay by an error in user’s program. (Enter a value in the range from 10ms to 6 s as the detecting time of the Watch Dog Timer in the Parameter.)

• While monitoring the scan time elapsed under operation, if it is detected to be over set time, the operation of a PLC is stopped immediately and all the output is reset.

• The ways to clear the error state of Watch Dog Timer are to resupply power or to convert mode to STOP mode.

• If an error in Watch Dog Timer occurs, Internal Flag F3.2 is set.

Checking whether Module Fixed or Unfixed

• This is the function used to detect whether the slot of the card built in a base is unfixed or connected incompletely.

• An error is indicated in case that a built module is unfixed or connected incompletely when power is ON.

Memory Check-Sum Error

• In case that there is an error in the flash memory of CPU or an error occurs in accessing Dual Port Ram, the error is indicated in Internal Flag Device F.

Battery Discharge

• The battery specifications are as follows.

• In case that the voltage of the battery is less than standard one, the Internal Flag F3.4 is set. At this time, the battery is to be replaced. If there is no battery, the programs are kept by an inside super capacitor for several minutes.

Power Failure

• A CPU module detects the instantaneous power failure when the voltage of input power is lower than the standard.

• If the CPU detects the instantaneous power failure, the following operation is processed to protect an error in action.

The case of instantaneous power failure is within 20ms

Open

The case of instantaneous power failure over 20ms

Open