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Reader/Writer under Operating Conditions
(3) Multiple Response
Multiple responses are sent per command when the following commands have been specified: Sin-
gle Repeat, FIFO Repeat, Multi-trigger, Multi-repeat, or Selective Access (for commands that com-
municate with Tags).
Host
Controller
5-1-3 ACK/NACK Control
When using ACK/NACK control, if the host does not receive a normal response, the Reader/Writer
will resend the response by either (1) when the host sends a NACK command to the Reader/Writer
or (2) when there is no response within a set period of time. Consequently, a response can be re-
ceived without communicating with a Tag again. The host checks that responses have been re-
ceived normally using the ACK/NACK commands, so response data can be communicated de-
pendably.
• Using ACK/NACK Control
If the host receives a normal response, it sends an ACK command to the Reader/Writer. The
Reader/Writer judges that the host has received a normal response, and enters a command-waiting
state. If, after the Reader/Writer has sent the response, an ACK is not received normally within the
time set using the time out setting, or a NACK is received, the Retry Flag is set and the last re-
sponse is sent again. The maximum number of response retries that can be made is nine.
(1) Host Receives a Normal Response and Sends ACK Command
(2) Host Cannot Receive a Normal Response and Sends a NACK Command
Host
Controller
(3) Host Did Not Send an ACK/NACK Command within the Timeout Period
Host
Controller
5-4
Command
Response
Host
Command
Controller
Command
Response
Command
Response
Response
Response
NACK
Error occurs
Timeout
Section 5-1
Response
ACK
ACK
Response
Retry
ACK
Response
Retry
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