Yaskawa VS-616G5 Profibus-DP Control Card SI-P - Manual (Page 16)

Page 16 VS-616G5 Option Instruction Manual: Profibus-DP Control Card SI-P
Example of handshaking protocol
After power-up or reinitialization, the PLC program has to clear the HS bit (bit 7) in the
handshaking register.
Below is a example of how handshaking is done. The arrows indicate which side has
control of the protocol.
Master
OUTPUT HS register
Option card
INPUT HS register
7 0
0 Initial setting
⇓
1
⇒
New MODBUS command to option card
⇓
1 Processing command
⇓
1
⇐
Response available
⇓
1 Idle
⇓
0
⇒
New MODBUS command to option card
⇓
0 Processing command
⇓
0
⇐
Response available
⇓
0 Idle