Appendix IR7000
72
Teledyne Analytical Instruments., - Rev. 3
A-3 RS-232 Communication Protocol
•
The RS-232 serial communication option allows back and forth
communication between the IR7000 and a remote PC. The
features of the IR7000 can be controlled and interrogated
through the serial port. It will output data in response to a
variety of requests.
•
There is a standard format for requests and commands sent to
the IR7000 and sent back from the instrument.
Each separate command or data packet is
transmitted as an ASCII string enclosed by a start
and stop character.
"(" is the ASCII start character — "STX"
")" is the ASCII stop character — "ETX"
•
All messages begin with the start character "(" followed by a 3-
character code. This code defines what the subject of the
message is. Any data that is required by the message is inserted
after the code and followed by the stop character ")". In many
messages, the code is the complete message and will be
followed by the stop character.
For example, a typical message exchange would be:
FROM user TO IR7000:
(e1C)
"(" is the start character.
e1C is the code requesting the set value of the span
calibration gas.
")" is the stop character.
FROM IR7000 TO user:
(e )
")" is the stop character.
e1C is the code stating that this is the set value of the
span calibration gas.
00100+ is the numerical value, with sign
")" is the stop character.
•
The serial port operates in half-duplex mode, either sending or
receiving data at any time. Sending information to the
instrument while it is still replying to a previous message will
disrupt the message.