Handbook
November 2011 / 59-UMC0071 / Issue 01
Mercury iTC
Page 100
REMOTE OPERATION
Original Instructions
7.4.9 Compatibility with IEEE-488.2
The Mercury iTC cryogenic environment controller supports IEEE-488.2.
7.4.10 Writing a reliable GPIB control program
The GPIB interface in the iTC has been designed to be very reliable. However the GPIB
control program must assume that data can be occasionally corrupted. The following
sections describe features that must be built into the control program to ensure
maximum reliability.
7.4.10.1 Timeouts
All commands that attempt to write or read data to an instrument must have a Timeout
facility built in. This ensures that the bus only waits a specified time period for a
response from an instrument.
When a timeout occurs, the controller must conduct a serial poll to attempt to discover
what has caused the timeout. If the serial poll also generates a timeout, the controller
must reset the interface using the Interface Clear (IFC) line. If a serial poll still fails, the
controller must assume that the iTC has lost power, has been disconnected, or has
failed in some way. The program must then alert the operator that a fault has occurred
and, if possible, continue operating the remaining instruments on the GPIB.
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