Transfer Of Decode Data - Symbol DS4308 Product Reference Manual

7 - 4 DS4308/DS4308P Digital Scanner Product Reference Guide

Transfer of Decode Data

The Decode Data Packet Format parameter controls how decode data is sent to the host. Set this parameter to
send the data in a DECODE_DATA packet. Clear this parameter to transmit the data as raw ASCII data.
NOTE When transmitting decode data as raw ASCII data, ACK/NAK handshaking does not apply regardless of
the state of the ACK/NAK handshaking parameter.
ACK/NAK Enabled and Packeted Data
The digital scanner sends a DECODE_DATA message after a successful decode. The digital scanner waits for
a programmable time-out for a CMD_ACK response. If it does not receive the response, the digital scanner
tries to send two more times before issuing a host transmission error. If the digital scanner receives a
CMD_NAK from the host, it may attempt a retry depending on the cause field of the CMD_NAK message.
Decoder
Data is captured
by decoder
ACK/NAK Enabled and Unpacketed ASCII Data
Even though the ACK/NAK handshaking is enabled, no handshaking occurs because the handshaking applies
only to packeted data. In this example the packeted_decode parameter is disabled.
Decoder
Data is captured
by decoder
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.
Decoder
Data is captured
by decoder
(1)
DECODE_DATA
(2)
CMD_ACK
message sent
ASCII data
(1)
DECODE_DATA
message sent
Host
Host
Host