SSI INTERFACE 10 - 5
ACK/NAK Disabled and Unpacketed ASCII Data
Data captured by the decoder is sent to the host.
Communication Summary
RTS/CTS Lines
All communication must use RTS/CTS handshaking as described in the Simple Serial Interface Programmer’s
Guide, p/n 72-40451-xx.
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.
Number of Data Bits
All communication with the decoder must use 8-bit data.
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 decoder.
Retries
When sending data, the host should resend twice after the initial send if the decoder 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 decoder replies with a NAK RESEND, the host resends the data. All resent
messages must have the resend bit set in the Status byte.
The decoder resends data two times after the initial send if the host fails to reply wit
h an ACK or NAK (if
ACK/NAK handshaking is enabled).
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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