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Appendix B: Using the GPIB Interface
Controller Commands
REMOTE Command
LOCAL LOCKOUT
Command
Polling Commands
B–2
The Preselector accepts the following commands from any GPIB controller.
To put the Preselector into remote mode, you must use your controller's
REMOTE command to set the GPIB REN line. The specific command you use
to do this will depend on your controller. If you send the REMOTE command as
an addressed command group (UAGC), the Preselector will go into remote mode
immediately.
To use a controller while leaving the Preselector in local mode, do not set the
REN line. The Preselector will then accept commands from the controller but
remain in local mode.
The Preselector lights the front-panel REMOTE LED to indicate that it is in
remote mode.
All Preselector switches, with the exception of the power switch, can be locked
out (made inoperative) by having your controller set the GPIB LOCAL
LOCKOUT state. Short of turning the Preselector off and on, or removing the
GPIB cable, the only way to cancel LOCAL LOCKOUT is to use your control-
ler's equivalent of the GO TO LOCAL command.
NOTE.
Put the Preselector into remote mode before using LOCAL LOCKOUT, or you
will not be able to control the Preselector manually or remotely.
Pressing the REMOTE/LOCAL switch will not turn on remote operation; it only turns
remote operation off.
Your controller can periodically check (poll) devices on the GPIB network to see
if a particular device needs service, or to determine which device sent a service
request (SRQ).
The controller can use a serial poll to access each device on the network
individually to read an 8-bit status byte. It then decodes the status byte to find
out what type of service the device needs.
The controller can use a parallel poll to quickly check if any devices require
service or to determine which device requested service. You can configure the
Preselector to respond to any one of 8 data lines during a parallel poll. The
Preselector will then assert its assigned data line during a parallel poll if it needs
service. If two devices share a data line, a serial poll of each device is necessary
to determine which one requires service.
Refer to your controller's manual for more information about GPIB polling.
2706 RF Preselector
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