Triton 9100 User Manual - Manual (Page 166)

M
ODEL
9100 U
SER
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ANUAL
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C
HANGES TO THE
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OMMUNICATION
S
PECIFICATION
The following changes have been made to Triton Standard Communications in order to support the new
functionality of this release.
Misc FID ‘ub’
The following new FID will be utilized (as described in the Triton Terminal Communications Protocol
and message Format Specification) to validate request and/or response messages. If the 'ub' FID is
present in the response message to the terminal, the terminal will validate the CRC and not the LRC of
the message when dial-up message protocol. The following describes the CRC calculation.
16-bit CRC.
4 ASCII characters that represent the CRC-16 two byte checksum.
Each character represents a 4-bit hexadecimal numeral (0-9, A-F).
Uses the ANSI CRC-16 error checking protocol standard.
For a request message the 16-bit CRC calculation starts with the first character after the STX, and ends
with the last character before the ETX, includes four ASCII zeros for the 'ub' field, and excludes the
LRC. The result is the four ASCII characters that is placed in the 'ub' field in msb to lsb order. The host
must also calculate the CRC by substituting the four ASCII character CRC result in the 'ub' field with
four ASCII zeros, then compare the results. The converse should be performed for the response
message.
The Triton TCP/IP protocol does not contain an STX, ETX, nor LRC, and includes a two-byte TCP/IP
message length in the CRC Calculation.