Reference Guide

SSI Interface
187
ACK/NAK Disabled and Packeted DECODE_DATA
In this example ACK/NAK does not occur even though packeted_decode is enabled because the
ACK/NAK handshaking parameter is disabled.
ACK/NAK Disabled and Unpacketed ASCII Data
Data captured by the digital scanner is sent to the host.
Communication Summary
ACK/NAK Option
Enable or disable ACK/NAK handshaking. This handshaking is enabled by default and Zebra recommends
leaving it enabled. Disabling this handshaking can cause communication problems, as handshaking is the
only acknowledgment that a message was received, and if it was received correctly. ACK/NAK is not used
with unpacketed decode data regardless of whether or not it is enabled.
Serial Response Time-out
The Serial Response Time-out parameter determines how long to wait for a handshaking response before
trying again, or aborting any further attempts. Set the same value for both the host and digital scanner.
Retries
When sending data, the host should resend twice after the initial send if the digital scanner does not
respond with an ACK or NAK (if ACK/NAK handshaking is enabled), or response data (e.g.,
PARAM_SEND, REPLY_REVISION). If the digital scanner replies with a NAK RESEND, the host resends
the data. All resent messages must have the resend bit set in the Status byte.
Decoder
Data is captured
by decoder
Host
(1)
DECODE_DATA
message sent
Decoder
Data is captured
by decoder
Host
(1)
ASCII data sent
note You can temporarily change the Serial Response Time-out when the host takes longer to process an ACK
or longer data string. Zebra does not recommend frequent permanent changes due to limited write cycles
of non-volatile memory.
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