Siemens SIMATIC S5-100U System Manual page 117

S5-100U
Time-Controlled Program Processing
Access to the interrupt PII is expressed by the "PB" or "PW" operand identifiers in a statement in
the time-controlled program.
The letter "L" represents the "Load" operation (see chapter 8).
• Byte-by-byte reading "PB <byte address>"
Example: Reading in the signal states of all
channels of an 8-channel digital input module
in slot 21
L PY 21
15
ACCU 1
High byte
• Word-by-word reading "PW <word address>"
Example: Reading in the analog value of
channel 2 of a 4-channel analog input module
in slot 1
L PW 76
15
ACCU 1
High byte
Interrupt-Driven Program Processing
• When a process interrupt occurs, only the data of the interrupt inputs, slots 0 and 1, is read into
the interrupt PII.
• Only this data of the interrupt PII is available to the interrrupt-driven program for evaluation.
• In a statement in the interrrupt-driven program, access to the interrupt PII is possible only with
the following operands: PB0, PB1, and PW0.
• If other parameters are specified, the CPU goes into the STOP mode and the "NNN" error
message is specified in the ISTACK. See section 5.2.
EWA 4NEB 812 6120-02b
0
Low byte
0
Low byte
Figure 6-10. Accesses to the Interrupt PII
Interrupt PII
Byte 21
Byte 76
Byte 77
Addressing
6-13