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5-26 QX Hawk Industrial Imager User Manual
Communication
ACK/NAK Protocol
The following are general outlines of the ACK/NAK protocol. Items that are framed by
brackets ( [ ] ) can either be disabled or enabled. LRC does not include STX, but it does
include preamble, postamble, and ETX.
Symbol Data Output
TX to host: [STX] [preamble] SYMBOL DATA [postamble] [ETX] [LRC]
Response from host: ACK/NAK. Sent when LRC, ETX, postamble, or timeout (waiting
for more data) are detected (if REQ is disabled) depending on what is enabled.
Commands from Host to Imager
TX to Imager: [STX] <command> [ETX] [LRC]
Response from Imager: ACK/NAK. Sent when LRC, ETX, or command-ending angle
bracket ‘>’ are received, depending on what is enabled.
Command Response from Imager to Host
TX to host: [STX] [preamble] COMMAND RESPONSE DATA [postamble] [ETX] [LRC]
Response from host: ACK/NAK. Sent when LRC, ETX, postamble, command-ending
angle bracket ‘>’, or timeout (waiting for more data) are detected, depending on what is
enabled.
As with Polling Mode <K140,5>, the imager can optionally perform the REQ and RES
event sequences in ACK/NAK mode. If the sender does not receive an ACK or NAK, it will
send REQ to request such a response (if enabled). When the sender receives an ACK, too
many NAKs, or times out (if already enabled), it will send a RES (if enabled) to terminate the
transaction.
Note:
See
ACK/NAK Data Flow Examples
in Appendix F for sample ACK/NAK communication
scenarios.
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