Siemens SIMATIC S5 Manual page 108
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STEP 5 Operations
Load Operation:
During loading, information is copied from a memory area, e.g., from the PII, into ACCUM 1.
The previous contents of ACCUM 1 are shifted to ACCUM 2.
The original contents of ACCUM 2 are lost.
Example: Two consecutive bytes (IB 7 and IB 8) are loaded from the PII into the accumulator.
Loading does not change the PII ( Figure 3-2).
Lost
information
Byte d
Byte c
Byte b
Byte a
Loading an input/output value with LPY/LPW operations:
Execution of an LPY/LPW operation triggers the following functions:
•
Reading of the value.
•
Exchange of data between the two subunits.
•
Comparison of the two values of subunits A and B.
If the values are not identical, the response depends on whether the relevant module is
interrupt-generating or not.
- Nonmatching values in the case of noninterrupt-generating DI modules.
To achieve minimum execution time, removal of the discrepancy is not interrogated. The
last valid value is taken as the standard value.
- Nonmatching values in the case of interrupt DI modules
Discrepancy analysis cannot be avoided here because 434 module interrupts are not stored
beyond the access.
•
Accesses in the AI address area
Accesses in this area are only permissible on the CP 523 implemented in single-channel connec-
tion.
3-12
ACCUM 2
Byte d
Byte c
Byte b
Byte a
0
IB 7
Figure 3-2. Execution of the Load Operation
ACCUM 1
Byte b
Byte a
L IB 7
0
IB 7
L IB 8
0
IB 8
S5-115F Manual
Information
from the PII
IB 7
IB 8
EWA 4NEB 811 6149-02
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