PLC Fatal Errors

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.

Error Code Description
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