Accessing The Process Image Output Table (Piq) - Siemens SIMATIC S5-100U System Manual

S5-100U
6.5.2

Accessing the Process Image Output Table (PIQ)

During a program cycle, data coming from the control program to the output modules is written into
the process image output table (PIQ). The data is transferred to the output modules in the following
data cycle.
Access to the PIQ is expressed by the operand identifiers "Q", "QB", or "QW" in a statement in
the control program.
The letter "T" identifies the "Transfer" operation (see Chapter 8). The "=" character assigns the
result of a logic operation (RLO) to the operand that follows the character (see chapter 8).
• Bit-by-bit writing
"Q <bit address>"
Example: Writing the signal state to
channel 6 of an 8-channel digital output
module in slot 4
• Byte-by-byte writing
"QB <byte address>"
Example: Writing the signal states to all
channels of an 8-channel digital output
module in slot 29
ACCU 1
• Word-by-word writing
"QW <word address>"
Example: Writing an analog value to
channel 2 of a 4-channel analog output
module in slot 6
ACCU 1
EWA 4NEB 812 6120-02b
= Q 4.6
T QB 29
15
High byte Low byte
T QW 116
15
High byte Low byte
Figure 6-9. Accesses to the PIQ
PIQ
Bit number
7 6 5 4 3 2 1 0
0
0
Addressing
Byte 4
Byte 29
Byte 116
Byte 117
6-11