B&K Precision 4079 - Manual - Manual (Page 45)

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SH1, AH1, T6, L4, SR1, RL1, PP0, DC1, DT1, E2, C0
4.4 Device Address
The GPIB address of the device may be set to any value from 0 to 31. The address may be changed from the front panel,
using the numeric keypad or the rotary encoder, or via the GPIB itself using the command:
:SYSTem:COMMunicate:GPIB:ADDRess
Setting the device to address 31 puts it in the 'off-bus' state. In this state it will not respond to messages on the GPIB. If the
device is in the REMS when set to address 31, an internal 'return-to-local' command will be given, setting the device to the
LOCS. If the device is in the RWLS, the 'return-to-local' command is ignored, and the device remains in the RWLS. The only
way to then re-establish communication with the device over the GPIB is to cycle the power, and to then change the address
to that required from the front panel.
4.5 Message Exchange Protocol
The device decodes messages using the Message Exchange Protocol (MEP) defined in IEEE 488.2. The following functions
implemented in the MEP must be considered:
4.5.1 The Input Buffer
The device has a 256-byte long cyclic input buffer. Decoding of remote messages begins as soon as the input buffer is not
empty, that is, as soon as the controller has sent at least one byte to the device. Should the input buffer be filled up by the
controller faster than the device can remove the bytes and decode them, the bus handshake is not completed until room has
been made for more bytes in the buffer. This prevents a fast controller from overrunning the device with data.
If the user has sent part of a Program Message, but not the Program Message Terminator, and he wishes to abort the message
decoding and execution, the Device Clear command may be sent, or front panel operation resumed (in REMS only).
4.5.2 The Output Queue
The device has a 100-byte long output queue in which it stores response messages for the controller to read. If at the time a
response message is formatted the queue contains previously formatted response messages, such that there are not enough
places in the queue for the new message, the device will put off putting the message in the queue until there is place for it.
The Status Byte MAV bit, when set, indicates that part or all of a response message is ready to be read.
4.5.3 Response Messages
The device sends a Response Message in response to a valid query. All queries return a single Response Message Unit. In
only one case is the Response Message generated when the response is read (as opposed to when the response is parsed), and
this is when querying Arbitrary Waveform data. All other queries generate the Response Message when they are parsed.
4.5.4 Coupled Commands
Coupled Commands are either commands whose execution validity depends on the value of other parameters, or commands
whose execution changes the value of another parameter. The execution of commands designated as being coupled is
deferred until all other commands in the same Program Message have been executed. The coupled commands are then
grouped together according to their functionality, and executed as a group. These groups of coupled commands are defined in
the MODEL 4076 and 4079: