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6
Remote Operation
6.1
Introduction
ILM may be remotely operated by means of its RS232 or GPIB interface. This allows a
computer to interrogate the instrument. For compatibility with other Oxford Instruments
products, a mode is available allowing the computer to control the instrument and
initiate sampling pulses. However it is not envisaged that this would be used for routine
operation.
6.2
Communication Protocols
ILM is always fitted with a Serial (RS232) interface. In addition, an optional GPIB (IEEE-
488) interface may be fitted. Details of the hardware communication protocols for the
two interfaces are given in sections 3.8 and 3.10 respectively.
The same command protocols are used for the Serial and GPIB interfaces.
All commands consist of a string of printing ASCII characters, terminated by a Carriage
Return character. A Line Feed character may optionally be sent after the Carriage Return
but is ignored by ILM.
Unless the command starts with a
"$"
(dollar) character, all commands will evoke a
response from ILM. The response will consist of a string of one or more printing ASCII
characters and will be terminated by a Carriage Return Character. This may optionally be
followed by a Line Feed character.
The response will normally be sent immediately following the command. If a front panel
button is pressed when the command is received, the response may be delayed until the
button is released. With the Serial Interface in use, the response will be transmitted
automatically as soon as it is available. With the GPIB interface, the response will be sent
when the instrument is next addressed to talk.
If the first character of a command is a
"$"
, the command will be obeyed but no
response will be sent (see section 6.5).
ILM will accept a command string at all times. If a computer linked by the serial (RS232)
port is unable to accept data from ILM at the full rate of the 9600 baud interface, the
"W" command may be used to instruct ILM to send more slowly.
6.3
Commands and Responses
Commands to ILM all consist of a single letter, optionally followed by a numeric
parameter, the whole being terminated by a Carriage Return. All commands are based
on Upper Case letters with mnemonic significance. The response sent by ILM varies
depending on the command. Usually it consists of the Command letter received,
followed by the value of any data requested. Where a command instructs ILM to carry
out an action rather than to send data, the command letter alone will be returned.
