Ack/Nack Control - Omron V700 Series Operation Manual

ACK/NACK Control

Multiple Responses
5-5

ACK/NACK Control

Use of ACK/NACK Control
The host receives a response normally and sends ACK.
The host sends NACK because a response is not received normally.
The host does not send ACK/NACK within a preset time-out period.
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If the single repeat, FIFO repeat, multiple trigger, or multiple repeat option is spe-
cified for communications with the ID Tag, multiple responses will be returned for
a single command.
Command
Host
Controller
When ACK/NACK control is being used and the host was not able to receive a
response normally, it is possible to receive a response even if communications
with the Tag are not executed again. ACK/NACK control verifies that the host
received the response normally, so response data communications can be per-
formed reliably.
The Controller returns a response for a command sent from the host and the
host sends ACK when the response to the command is received. Then the Con-
troller determines that the host has received the response normally and waits for
the next command. If the Controller does not receive ACK within a preset time-
out period or the Controller receives NACK, the Retry Flag is set and the re-
sponse is returned to the Controller again. This is repeated at least nine times.
Host
Controller
Host Command
Controller
Host Command
Controller
Response Response
Command
Response
NACK
Response
Error results
Response
Time out
Section 5-5
Response Response
ACK
ACK
Response
Retry
ACK
Respons
e
Retry
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