Siemens S7-200 User Manual download pdf (Page 12)

The PLC Cycle (1)

All SIMATIC programmable controllers usually work in a cyclical manner. In this cyclical

operation the switch statuses are read at the inputs and stored in the process input

image (PII). This information is subsequently used to feed and process the control pro-

gram.

Process Input

Image: PII

Revision

What you know already...

- A Few Words of Revision

- Here are the Bits

- Current Flow in the Ladder Diagram

- The PLC Cycle

Inputs

Outputs

PIQ = Process-image output table (output register)

PII = Process-image input table (input register)

STEP-7 program

• Bit memories

•Timers

• Counters

• .........

Network 1 Motor on/off

Network 2 Direction rever-

sal of rotation

Latching Revision

Pulse-Oper-

ated Switch

Off-Delay

Timer

Sequencer Appendix

1 2 ... 7 8 9 10 11 12 13 14 15 16 17 ... 73 74

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Siemens S7-200 User Manual Page 12