Technical data

Operation code error
(OB 29)
An operation code error is detected by the CPU during the execution
of a STEP 5 program when an operation is programmed that does not
belong to the STEP 5 set of operations for the CPU 928B (e.g. RU and
SU operations can be programmed at the programmer but cannot be
interpreted by the CPUs 928B, 928, 922 (R processor) and 921
(S processor) in the S5 135U).
If the CPU detects an illegal operation code, the execution of the user
program is interrupted and organization block
OB 29 is called, if it is
loaded
When OB 29 is called, ACCU 1 contains additional information that
defines the error in greater detail.
Error identifier
ACCU-1-LACCU-2-L
Explanation
1811H —
Operation with illegal OP code
1812H —
Illegal OP code for an operation in which
the high byte of the first operation word
contains the value 68H
1813H —
Illegal OP code for an operation in which
the high byte of the first operation word
contains the value 78H
1814H —
Illegal OP code for an operation in which
the high byte of the first operation word
contains the value 70H
1815H —
Illegal OP code for an operation in which
the high byte of the first operation word
contains the value 60H
Caution
An operation code error should not be acknowledged: the CPU
does not recognize whether the incorrect operation is a single
word or multiword operation. Once the CPU has processed
OB 29, it attempts to continue the program at the next operation
word. If this is the second word of a multiword operation, it either
detects a further operation code error or executes this word as a
valid operation, which can cause a variety of
program errors.
Table 5-18 BCF operation code error
5
Errors in RUN and in RESTART
CPU 928B Programming Guide
C79000-B8576-C898-01 5 - 41