Fatal errors cause the PLC to stop the execution of your program. Depending on the severity of the error, a fatal error can render the PLC incapable of performing any or all functions. The objective for handling fatal errors is to bring the PLC to a safe state from which the PLC can respond to interrogations about the existing error conditions.
The PLC performs the following tasks when a fatal error is detected.
·Changes to STOP mode
·Turns on both the System Fault LED and the Stop LED
·Turns off the outputs
The PLC remains in this condition until the fatal error is corrected. The table shown below provides a list with descriptions for the fatal error codes that can be read from the PLC.
STEP 7-Micro/WIN 32 displays the error codes generated by the PLC (for example, 0001, 000C), along with a brief description, in the PLC Information dialog box. To access this dialog box, select the menu command PLC > Information….
Once you have corrected the conditions that caused the fatal error, you must restart the PLC by either of the following methods.
·Power-cycle the PLC, or
·Move the mode switch from TERM or RUN to the STOP position. (The mode switch functions in this way only when the PLC has a fatal error and the fault light is on.)
Restarting the PLC clears the fatal error condition and causes power-up diagnostic testing. If another fatal error condition is found, the PLC sets the System Fault LED again; otherwise, the PLC begins normal operation.
There are several possible error conditions that can render the PLC incapable of communication, in which case you cannot view the PLC error code. This type of error indicates a hardware failure requiring the PLC module to be repaired; it cannot be fixed by changes to the program or by clearing the PLC memory.
|0000||No fatal errors present|
|0001||User program checksum error|
|0002||Compiled ladder program checksum error|
|0003||Scan watchdog timeout error|
|0004||Internal EEPROM failed|
|0005||Internal EEPROM checksum error on user program|
|0006||Internal EEPROM checksum error on configuration parameters|
|0007||Internal EEPROM checksum error on force data|
|0008||Internal EEPROM checksum error on default output table values|
|0009||Internal EEPROM checksum error on user data, DB1|
|000A||Memory cartridge failed|
|000B||Memory cartridge checksum error on user program|
|000C||Memory cartridge checksum error on configuration parameters|
|000D||Memory cartridge checksum error on force data|
|000E||Memory cartridge checksum error on default output table values|
|000F||Memory cartridge checksum error on user data, DB1|
|0010||Internal software error|
|0011||Compare contact indirect addressing error|
|0012||Compare contact illegal value error|
|0013||Memory cartridge is blank or the program is not understood by this PLC|