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1 General Overview
05.91
1.3.3 Provision of I/O signals, process image
Process image PII, PIQ
The image of the inputs in the I area is called the process input image (PII) and the image of
the outputs in the Q area is called the process output image (PIQ).
At the start of a PLC cycle (before OB 1 is activated), the PLC operating system reads the in-
puts of the digital I/O devices and updates the PII. The PII then remains stable for the duration
of one PLC cycle (provided that the PLC user program does not change it). The change of an
input signal appears in the PII after one PLC cycle at the latest.
At the end of a PLC cycle (after OB 1 has been processed), the PLC operating system reads
the PIQ and switches the output signals accordingly. If the PLC user program changes a signal
in the PIQ, the relevant output signal thus follows after one PLC cycle at the latest.
Provision of I/O signals
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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 a a a a a a a a a a a a a a a
PLC operating
system
I/O modules
of machine
I/O devices
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 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 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
COM area
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 a a a a
a a a a a a a a a a a a
Link RAM
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 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 a a
a a a a a a a a a a a
a a a a a a a a a a a
PLC cycle
start
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 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 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
PLC cycle
end
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 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 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 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 a a a a
E.g. optical fibre conductor
I/O submodules (max. 4)
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 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 a a a a a a a a a a a a a a a a
Machine signals
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 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 a a a a
Other signals
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
IB 0
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
IB 127
a a a a a a
a a a a a a
a a a a a a
a a a a a a
QB 0
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 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 a a a a a a
a a a a a a a a a a
Q area
(PIQ)
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 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 a a a a a a
a a a a a a a a a a
I area
(PII)
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
QB 127
a a
a a
aa
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
1–22
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SINUMERIK 880 (PJ)