YASKAWA SI-P3 Technical Manual page 21

■ Flow Chart
Figure 8 illustrates the handshaking function when using a MEMOBUS/Modbus message.
Figure 7
Power ON or
re-initialization
NO
NO
YASKAWA ELECTRIC SIEP C730600 42A YASKAWA AC Drive-Option Card PROFIBUS-DP Technical Manual
PROFIBUS-DP Master
START
Clears the handshaking
register HS bit to "0"
Sends a new message
YES
Creates a command message.
Toggles handshaking
register HS bit <1>
Sends to slave
INDATA HS =
YES
Handles the response
Figure 8 MEMOBUS/Modbus Message Flow Chart
SI-P3 Card
START
Initialization
Clears handshaking
register HS bit to "0".
<1> "Toggle" means changing
Receives for the master
Command message
Normal
Command executed
Creates a response message
Toggles handshaking
register HS bit <1>
Sends to master
7 Conventional Formats
the HS bit status from
0 to 1 or from 1 to 0.
Abnormal
Command not executed
Creates a response
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