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In COMMAND mode, bus commands can be placed on the bus and sent to all
devices. These commands have the same meaning regardless of the kind of device.
Each device is designed to respond to those commands that have a useful meaning to
the device and will ignore all others. The operating manual of each device will state
those commands it can recognize.
Type
Mnemo ASC
-------
--------- ------
Universal
LLO
Universal
DCL
Universal
PPU NAK
Universal
SPE
Universal
SPD
Address
SDC
Address
GTL
Address
GET
Address
PPC
Address
TCT
Unaddress
UNL
Unaddress
UNT
Some IEEE-488 devices have the ability to request service from the controller. A
device may request service when it has completed a measurement, or when it has
detected a critical condition, or for other reasons. An IEEE-488 device requests
controller service by setting the SRQ line low. The controller has to determine when
and how a service request will be serviced.
The following sequence is used to respond to a service request:
1) The controller checks for the presence of a service request.
6 8
PCL-848AB
Bus Command Table
Bex
Purpose
-----
--------------------------------------------------------
DC1
11
Local Lockout. Disable front panel local key of
the devices.
DC4
14
Device Clear. All devices are set to a known
state.
15
Parallel Poll Unconfigure.
CAN
18
Serial Poll Enable.
EM
19
Serial Poll Disable.
EOT
04
Selective Device Clear. Clear the listeners to a
known state.
SOE
01
Go To Local. Set all listeners into local mode.
BS
08
Group Execute Trigger. Trigger all listeners on
the bus.
ENQ
05
Parallel Poll Configure. Configure a device to
respond to parallel poll.
ET
09
Take Control. Transfer control to another
device.
?
3F
Unlisten. Unaddress the current listeners.
_
SF
Untalk. Unaddress the current talker.
User's Manual
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