BECKHOFF C1120 - Manual (Page 28)

C1120 S5 to II/O-Lightbus Interface Beckhoff II/O-Lightbus System
Page 28 of 52 Version 2.1 Date 27.06.97
How to program a parallel channel communication:
a.) Request of the Siemens PLC to the C1120 interface (master is transmitter)
1. Write function number to PB/PY 252
2. Write argument 1 to PB/PY 251
3. Write argument 2 to PB/PY 250
4. Set strobe bit PB/PY 253.7
5. Wait for C1120 acknowlege bit PB/PY 253.6 to be "1" (function is started by
C1120 interface)
6. Reset strobe bit PB/PY 253.7
7. Wait for C1120 acknowlege bit PB/PY 253.6 to be "0" (end of handshake cycle).
b.) Answer of the C1120-interface to the Siemens PLC (master is receiver)
1. C1120 sets strobe bit PB/PY 253.7 after receiption of a function call as described
under a): Valid data bytes are ready to be read.
2. Read data: The function number is represented in PB/PY 252,
argument 1 is represented in PB/PY 251,
Argument 2 is represented in PB/PY 250.
3. Set acknowlege bit PB/PY 253.6 at end of data read.
4. C1120 interface resets strobe bit PB/PY 253.7.
5. End handshake cycle by resetting acknowlege bit PB/PY 253.6.
All steps of the handshake have to take place in the above described order. All function calls
are carried out with full handshake.