Microscan MS-890, User Manual, Page: 52 / 308

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MS-890 Industrial Automation Scanner User Manual
ACK / NAK Options
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 Scanner
TX to Scanner: [STX] <command> [ETX] [LRC]
Response from Scanner: ACK/NAK. Sent when LRC, ETX, or command-ending angle
bracket ‘ > ’ are received, depending on what is enabled.
Command Response from Scanner 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 scanner 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.
Definition:
These parameters take effect for ACK/NAK <K140,4> on the main RS-232 or
RS-422 ports (not on the Auxiliary Port), and are completely independent of
the Polling Mode Options <K148> .
The scanner 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)
0x00 (disabled)
REQ: (Request)
0x00 (disabled)
STX: (Start of Text)
0x00 (disabled)
ETX: (End of Text)
0x00 (disabled)
ACK: (Acknowledge)
0x06
NAK: (Negative Acknowledge)
0x15