MicroHAWK Engine Integration Guide 4-7
Communications
ACK/NAK Options
RES-NAK Defaults
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 Reader
TX to Reader: [STX] <command> [ETX] [LRC]
Response from Reader: ACK/NAK. Sent when LRC, ETX, or command-ending angle
bracket ‘>’ are received, depending on what is enabled.
Command Response from Reader 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 reader 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 trans-
action.
Note:
See
ACK/NAK Data Flow Examples
for sample ACK/NAK communication scenarios.
Definition:
These parameters take effect for
ACK/NAK
<K140,4>
on the main RS-232
port and are completely independent of the
Polling Mode Options
<K148>
.
The reader always follows the protocol in both directions (to and from the
host). There is no option to disable it from either direction.
Serial Cmd: <K147,RES,REQ,STX,ETX,ACK,NAK>
RES: (Reset) 00 (disabled)
REQ: (Request) 00 (disabled)
STX: (Start of Text) 00 (disabled)
ETX: (End of Text) 00 (disabled)
ACK: (Acknowledge) 06
NAK: (Negative Acknowledge) 15
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