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Introduction to STEP 5
OB24
Response to timeout when updating the process I/O image or the interprocessor
communication flag
If a timeout occurs during updating of the process I/O or the interprocessor com-
munication flag, the absolute module address is stored in system data word 103 (EACE
and OB24 is called. If OB24 does not exist, the CPU goes to STOP with QVZ.
OB27
Response to substitution errors
A substitution error (SUF) can occur when the formal parameters of a function block are
changed after the block is called ("JU FBx", "JC FBx").
The operating system interrupts the control program when a substitution error has been
detected and then executes OB27 instead of the substitution operation. If OB27 does not
exist, the CPU goes to STOP with the ISTACK error code "SUF".
OB32
Response to transfer errors
A transfer error (TRAF) occurs under the following circumstances:
-
When data words are accessed without previously calling a data block (C DB).
-
If the parameter is longer than the data block opened in the case of the operations
L DW; T DW; TBD; TBN D; SU D; RU D; etc.
-
If there is not sufficient user memory available to generate the specified data block in
the case of the G DB (Generate Data Block).
Response to transfer error: The operating system interrupts processing of the operation
where the transfer error occurred and processes OB32 instead. If OB32 does not exist, the
CPU goes to STOP with the ISTACK error code "TRAF".
OB34
Response to the BAU (battery failure) signal
The PLC continuously checks the status of the battery in the power supply. If battery
failure (BAU) occurs, OB34 is processed before each cycle until the battery has been
replaced and the battery failure indicator on the power supply has been acknowledged
(RESET key). You program the repsonse to battery failure in OB34. If OB34 has not been
programmed, no response results.
Additional OBs which offer you operating functions, are described in Chapter 11;
OB160
Time loop
OB251
PID control algorithm
OB254
Reading in digital inputs (only in the case of CPU 944)
OB255
Outputting the process I/O image of the outputs (PIQ) to the outputs (only in the case of
CPU 944)
7-24
S5-115U Manual
)
H
EWA 4NEB 811 6130-02b
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