Oxford Instruments Mercury iTC, Руководство пользователя

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Handbook
November 2011 / 59-UMC0071 / Issue 01
Mercury iTC
Page 99
REMOTE OPERATION
Original Instructions
7.4.4.4 Status byte update rate
The iTC updates the status byte every millisecond. If the status byte is read within 1 mS
of reading data from the interface, the BAV and MAV bits may still be set. If these bits
are found to be set immediately after reading data, the GPIB controller should read the
status byte again to confirm if data is still remaining.
7.4.5 Use of the service request line
The iTC issues a service request (by pulling the SRQ line) when a complete message is
available to be read. The MAV bit will be set at the same time. The exception is when
the iTC is already configured to talk. Since the GPIB controller is already reading data
from the iTC, a service request is not required.
The GPIB controller can be programmed to monitor the SRQ line and to only read data
from the iTC when the SRQ line is asserted. This is more efficient that reading the status
byte at regular intervals.
7.4.6 Use of the device clear function
When the iTC receives a GPIB Device Clear message, it empties all communication
buffers. It does not reset any of the temperature control functions. Device Clear can thus
be safely used to empty the communication buffers of any unread messages.
Device Clear can be sent by either the GPIB DCL message (which clears all connected
devices), or by the GPIB SDC message (which only clears the addressed device).
7.4.7 Use of the interface clear function
When the iTC receives a single-line IFC message, it clears the GPIB interface functions
as specified by IEEE-488.1. The command does not clear any pending data in the
buffers. The command does not affect any temperature control functions.
7.4.8 Non-implemented features of the GPIB
The GPIB Remote Enable (REN) line is only used to alert the iTC to the presence of an
active controller. It is not used for switching between Local and Remote modes. Use the
C command to switch between local and remote modes. This is simpler than the REN
command and is also compatible with RS232 operation.
The GPIB Local Lockout and Go To Local commands have no effect on the iTC. Use the
C command to perform these actions.
The iTC does not respond to a parallel poll request. Because the GPIB interface uses
open-collector data-buffers, the iTC can co-exist on a GPIB that has other instruments
that do have a parallel poll capability.