Addressing S5-115F Manual
5.3.1 Accessing the PII
In the ”RESTART” mode and at the beginning of program scanning, the digital and analog input
module signal states are written into the PII. The input images of subunit A and subunit B are then
exchanged and compared. Any differences in input information are subjected to discrepancy
analysis to establish whether there is a hardware error in the relevant input module or whether
the deviation is tolerable. A standard value is generated from tolerable input value differences.
This uniform value allows both subunits to execute identically.
The statements in the control program use a particular address to indicate what information is
currently needed. The processor then reads the data that was current at the beginning of program
scanning and works with it.
High byte
015
Reading bit by bit
for binary operations:
A I 2.2
7 6 5 4 3 2 1 0
Bit No.
PII
Byte 2
Reading byte by byte
for loading into ACCUM 1:
L IB 12
Byte 12
Reading word by word
for loading into ACCUM 1:
L IW 40
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
ACCUM 1
a
Low byte
015
Byte 40
Byte 41
ACCUM 1
High byte Low byte
Figure 5-6. Accessing the PII in the Case of Digital Input Modules
5-6
EWA 4NEB 811 6148-02
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