Serial Interface Manual
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TLS2 Monitoring Systems
Part No. 577013-767, Revision H
4
6.0
RESPONSE MESSAGE FORMAT
There are two types of response message formats: computer (or packed data format) and display format.
Each format uses a different surrounding envelope of control characters.
6.1
COMPUTER FORMAT
The computer format is a stream of data without any formatting characters; i.e., carriage return, line feed,
spaces, labels, etc. The message format is as follows:
SOH
Function Code
Data Field
&&
Checksum
ETX
SOH is a fixed Control-A character (ASCII 01), and it indicates the beginning of the message.
The function code is identical to the received command message function code.
The data field contains the response message which is described in subsequent sections.
The "&&" is a fixed tag character which indicates that the checksum immediately follows.
The Checksum is a series of four ASCII-hexadecimal characters which provide a check on the integrity
of all the characters preceding it, including the control characters. The four characters represent a 16-bit
binary count which is the 2's complemented sum of the 8-bit binary representation of the message
characters after the parity bit (if enabled) has been cleared. Overflows are ignored. The data integrity
check can be done by converting the four checksum characters to the 16-bit binary number and adding
the 8-bit binary representation of the message characters to it. The binary result should be zero.
ETX is a fixed Control-C character (ASCII 03), and it indicates the end of the message.
6.2
DISPLAY FORMAT
The display format is intended for display on a CRT or printer. It includes all the necessary formatting
characters such as carriage returns, line feeds, nulls, spaces, labels, etc. The message format is as
follows:
SOH
Function Code
Data Field
ETX
See subsequent sections for a description of the data field response messages.
