Ametek Thermox TM2000, User Manual

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A-2 | Thermox TM 2000 Oxygen Analyzer
Command Message Format
The command message format is as follows:
Where:
The Start Character is the greater than character (“>”, which is ASCII
decimal character 62 or hexadecimal character 3E).
The Node Address is from 00-FF, and is represented as two hex ASCII
characters. Each controller has a unique node address (see the “Communi-
cation/Node Address” section in the Setup Key chapter for help on speci-
fying node addresses for controllers). Note, however, that the maximum
number of controllers that can be connected on the network is 32.
The Command Letter is from ASCII A-Z (upper case only).
Data is a string of characters whose meaning depends on the command
(see below) and where the number of characters returned also depends
on the command. Limit is 20 characters.
The Checksum is the sum of all the preceding characters (excluding the
>> character) - modulo 256.
The End Character is a carriage return (equivalent to ASCII decimal char-
acter number 13).
The system disables any checking of the checksum if the checksum
character is equal to ?? (?? is equivalent to 2 ASCII 63 characters).
This makes testing by the programmer easy, but it is strongly recom-
mended that the integrity check is enabled in the final system.
NOTE

Start Character Node Address Command
Letter
Data Checksum End Character
“>” (AScii deci-
mal character 6) 2 hex Ascii
characters
(00-FF) (See com-
mands sec-
tion for list of
commands (n characters
- depends on
command) 2 hex AScii
characters
(sum except
the “>” char-
acter cariage return
(AScii decimal
13)