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5-1
Alarm Indicators
There are three indicators on the front of the CPU that provide visual indica-
tion of errors in the PC. The power indicator (POWER) indicates errors due
to incorrect application of power to the PC; the error indicator (ERROR) indi-
cates fatal errors (i.e., ones that will stop PC operation); the link indicator
(LINK) indicates PC link errors.
WARNING
The PC will turn ON the error indicator (ERROR), stop program execution, and
turn OFF all outputs from the PC for most hardware errors and for fatal software
errors. PC operation will continue for all other errors. It is the user’s responsibility
to take adequate measures to ensure that a hazardous situation will not result
from automatic system shutdown for fatal errors and to ensure that proper
actions are taken for errors for which the system is not automatically shut down.
System flags can be used to program proper actions.
5-2
Reading and Clearing Errors and Messages
System error messages can be displayed on the Programming Console.
On the Programming Console, press the CLR, FUN, 6, 1, and MON keys. If
there are multiple error messages stored by the system, the MON key can be
pressed again to access the next message. If the system is in PROGRAM
mode, pressing the MON key will clear the error message, so be sure to write
down all message errors as you read them.
It is not possible to clear an error or a message while in RUN mode; the PC
must be in PROGRAM mode.
When all messages have been cleared, “CHECK OK” will be displayed and
the ERROR LED will turn OFF.
If a “COMM ERR” occurs, the Programming Console will ignore any key op-
eration other than CLR, so press CLR to clear the communication error and
allow access via the PC Link to CPU Unit #0. Ensure the correct connection
of cables between the Units.
Note If a memory error occurs in the PC, the Programming Console may not func-
tion properly if the program is transferred from the PC to the Programming
Console. Perform a program comparison between the transferred program
and the program in the PC to see if the programs are the same.
5-3
Error Messages
There are basically two types of errors for which messages are displayed:
programming errors and fatal operating errors.
The type of error can be quickly determined from the indicators on the CPU,
as described below for the two types of errors. If the status of an indicator is
not mentioned in the description, it makes no difference whether it is lit or not.
After eliminating the cause of an error, clear the error message from memory
before resuming operation.
The following error messages appear if an error occurs during programming.
The Programming Console will be in PROGRAM mode. The POWER indica-
tor will be lit and the RUN indicator will not be lit for either of these.
Programming Errors
Error Messages
Section 5-3