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5.6.3
OB 23/24, OB 28/29:
Timeout Error (QVZ)
OB 23
OB 24
Extension of the execution
time
CPU 948 Programming Guide
C79000-G8576-C848-04
Causes of Error and Reactions of the CPU
A timeout error occurs when an addressable memory area does not
respond to write or read accesses with the ready signal ("RDY")
within a specific time after being addressed. This time is monitored by
the hardware. A defective module or the removal of a module during
operation of the programmable controller can cause a timeout error.
The following timeout errors interrupt the user program, jump to
system program error handling, and call the appropriate blocks if they
are loaded:
QVZ with direct I/O access:
Cause of error
Timeout error in the user
program during direct access via
the S5 bus to an IP, COR, or
to a peripheral module (e.g.,
with load and transfer operations
"L/T P..." or "L/T Q...").
Cause of error
Timeout error during update of
the process image input/output
tables or during transfer of
interprocessor communication
flags.
With calling OB 23 or OB 24 a timeout error increases the execution
time of the STEP 5 operation which caused the timeout when the
program is resumed:
extension = "acknowledgement monitoring time + time of error
handling in the system program + processing time if error OB is
called".
Reaction to error
If OB 23 is not loaded, the
system program continues the
processing of the user program.
Reaction to error
If OB 24 is not loaded, the
system program continues
processing of the user program.
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