Chapter 28
Troubleshooting Faults
28–5
Error Code
(Hex)
Description
Probable Cause
Recommended Action
0021
A remote power failure of an expansion I/O
rack has occurred.
Note: A modular system that encounters
an overvoltage or overcurrent condition in
any of its power supplies can produce any
of the I/O error codes listed on pages 28-8
to 28-10 (instead of code 0021). The
overvoltage or overcurrent condition is
indicated by the power supply LED being
off.
ATTENTION:
Fixed and FRN 1 to 4
SLC 5/01 processors - If the
remote power failure occurred
while the processor was in the Run
mode, error 0021 will cause the
major error halted bit (S:1/13) to be
cleared at the next powerup of the
local rack.
SLC 5/02 processors and FRN 5
SLC 5/01 processors - Power to
the local rack does not need to be
cycled to resume the Run mode.
Once the remote rack is
repowered, the CPU will restart
the system.
!
Fixed and FRN 1 to 4 SLC 5/01
processors: Power was removed or the
power dipped below specification for an
expansion rack.
SLC 5/02 processors and FRN 5 and
higher SLC 5/01 processors: This error
code is present only while power is not
applied to an expansion rack. This is the
only selfclearing error code. When power
is reapplied to the expansion rack, the
fault will be cleared.
Fixed and FRN 1 to 4 SLC 5/01
processors: Cycle power on the local
rack.
SLC 5/02 processors and FRN 5 and
higher SLC 5/01 processors: Reapply
power to the expansion rack.
0022
The user watchdog scan time has been
exceeded.
•
Either Watchdog time is set too low for
the user program, or
•
user program caught in a loop.
•
Either increase the watchdog timeout in
the status file (S:3H), or
•
correct the user program problem.
0023
Invalid or nonexistent STI interrupt file.
•
Either an STI interrupt file number was
assigned in the status file, but the
subroutine file was not created, or
•
the STI interrupt file number assigned
was 0, 1, or 2.
•
Either disable the STI interrupt setpoint
(S:30) and file number (S:31) in the
status file, or
•
create an STI interrupt subroutine file
for the file number assigned in the
status file (S:31). The file number must
not be 0, 1, or 2.
0024
Invalid STI interrupt interval.
The STI setpoint is out of range (greater
than 2550 ms, or negative).
•
Either disable the STI interrupt setpoint
(S:30) and file number (S:31) in the
status file, or
•
create an STI interrupt routine for the
file number referenced in the status file
(S:31). The file number must not be 0,
1, or 2.
0025
Excessive stack depth/JSR calls for the
STI routine.
A JSR instruction is calling for a file
number assigned to an STI routine.
Correct the user program to meet the
requirements and restrictions for the JSR
instruction, then reload the program and
run.
