Ack/Nak Options - Microscan MS-4 User Manual

ACK / NAK Options
Definition: These parameters take effect for ACK/NAK
RS-422 ports (not on the Auxiliary Port), and are completely independent of
the Polling Mode Options <K148>.
The Imager 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-NAK Defaults
RES: (Reset)
REQ: (Request)
STX: (Start of Text)
ETX: (End of Text)
ACK: (Acknowledge)
NAK: (Negative Acknowledge)
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
scenarios.
Note: See USB HID Interface
MS-4 Imager User's Manual
00 (disabled)
00 (disabled)
00 (disabled)
00 (disabled)
06
15
in Appendix D for sample ACK/NAK communications
on page 3-23 for protocol information relating to USB.
Communications
<K140,4> on the main RS-232 or
3-7