Accessing The Process Image Input Table (Pii) - Siemens S5-100U User Manual

Addressing
6.5.1

Accessing the Process Image Input Table (PII)

During a data cycle, data is read into the process image input table (PII) from input modules (see
section 2.2.2 - Data Cycle). This data is available to the control program for evaluation in the next
program processing cycle.
Access to the PII is expressed by the operand identifiers "I", "IB", or "IW" in a statement in the
control program.
The letter "L" identifies the "Load" operation (see chapter 8). The letter "A" identifies the "AND
logic" operation (see chapter 8).
• Bit-by-bit reading "I <bit address>"
Example: Reading in the signal state of
channel 2 of a 4-channel digital input module
in slot 2
• Byte-by-byte reading "IB <byte address>"
Example: Reading in the signal states of all
channels of an 8-channel digital input module
in slot 12
ACCU 1
• Word-by-word reading "IW <word address>"
Example: Reading in the analog value of
channel 3 of a 4-channel analog input module in
slot 4
ACCU 1
Always set to "0"
6-10
A I 2.2
L IB 12
15
High byte Low byte
L IW 102
15
High byte Low byte
Figure 6-8. Accesses to the PII
PII
Bit number
7 6 5 4 3 2 1 0
0
0
EWA 4NEB 812 6120-02
S5-100U
Byte 2
Byte 12
Byte 102
Byte 103