Serial Interface Manual
TLS4/TLS-450 Monitoring Systems
Part No. 577013-950, Revision L
5
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 numbers 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
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 programmable if enabled via the S53100f command. If it is disabled, the ETX is a fixed
Control-C character (ASCII 03). Caution should be taken before changing the ETX character,
because it affects the transmitted messages on ALL communications ports of the system, and
additional host devices may be connected to other ports which expect the ETX to be a Control-C.
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.