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(3） Data transmitted by master (control abort process)
① Master sends ENQ code to slave.
② Since ACK code cannot be sent, slave sent NACK code to master.
③ Sequence is repeated 3 times in attempts to retransmit.
After receiving the 3rd successive NACK code, communications control is aborted
(4） Data transmitted by master (data error process)
① Session starts when ENQ is sent from master to slave.
② Slave acknowledges by returning ACK to master.
③ Master sends data, but slave detect error (framing, over-run error).
④ Slave detects error and does not accept data.
⑤ Sequence 3 and 4 repeats, then master transfers normal data.
⑥ Slave detects normal data and returns ACK code to master to end the session.
HITACHI
Master (PC)
1
2
3
ENQ code (05H)
NACK code
(
15H
)
ENQ code (05H)
NACK code
(
15H
)
ENQ code (05H)
NACK code
(
15H
)
ENQ code (05H)
NACK code
(
15H
)
Slave
(KP-F500PCL/SCL
KP-FR500PCL/SCL)
HITACHI
Master (PC)
1
2
3
ENQ code (05H)
ACK code
(
06H
)
Send data (error occurs)
Send data (error occurs)
Send data (data normal)
ACK code
(
06H
)
4
5
6
3 second
elapse
3 second
elapse
Slave
(KP-F500PCL/SCL
KP-FR500PCL/SCL)