B-1
Model 979 Series Helium Mass Spectrometer Leak Detector
DRAFT 9/15/03
Appendix B. Communications Protocol
This appendix defines the technical specifications for the RS-232 protocol to be used with
the 979 Leak Detector.
B.1 Protocol (RS-232)
RS-232 ports operate at 9600 baud, 8 bits, no parity, and one stop bit.
All characters transmitted to the leak detector are echoed by the leak detector. Commands,
inquiries, and strings of both commands and inquiries must be terminated by a carriage
return <CR>; the carriage return is echoed as a space character.
The maximum length of the input is 80 characters; if no carriage return has been received
before the 80th character, execution of the command string begins anyway. Words that
begin with the
?
character are inquiries for the controlling device to determine the current
state or value of a leak detector parameter.
Words that begin with
PUT
are commands for the controlling device to set the current state
or value of a volatile leak detector parameter. Words that begin with
INIT-
are commands
for the controlling device to set non-volatile leak detector parameters. Other commands do
not require a parameter and do not begin with any special character(s).
Successful inquiries respond with data, followed by a space, then:
ok
<CR><LF>, as speci-
fied in the tables of this appendix. Unsuccessful inquiries respond with the offending
inquiry followed by a space, then:
#?
<CR><LF> (line feed, <LF>).
Inquiries, parameters, and commands can be concatenated. Each word or numeric parame-
ter is followed by one or more spaces. The string is terminated by a <CR>, which causes
execution to begin. Successful strings respond with the specified data for the input inquiries
in the order the inquiries were issued, followed by:
ok
<CR><LF>. Unsuccessful strings
respond with the
first
offending command followed by a space, then:
#?
<CR><LF>. All
commands and inquiries following the failed word are ignored; all parameters are dis-
carded.
Table B-1 on page B-5, Table B-2 on page B-7, Table B-3 on page B-9, and Table B-4 on
page B-9 outline the available control and query commands.
Summary of Contents for 979 Series
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