Fluke 9640A Series, Instruction Manual

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SCPI and IEEE Bus Descriptions
Program and Response Messages
4B
4B-7
Sequential and Overlapped Commands
SCPI defines two classes of commands: sequential and overlapped commands. All
commands in the Instrument are sequential, that is one command finishes before the next
command executes.
Remote Local Protocol
Definitions Remote Operation
When an instrument operates in remote, all local controls, except the
Go To Local
soft
key and

key, are disabled.
Local Operation
An instrument operates in local when it is not in remote mode as defined above.
Local Lockout
In addition to the remote state, an instrument can be set to remote with ‘local lockout’.
This disables the return-to-local button. In theory, the state local with local lockout is also
possible; then, all local controls except the return-to-local key are active.
The Instrument in Remote Operation
When the Instrument is in remote operation, it disables all its local controls except the
Go
To Local
soft key.
The Instrument in Local Operation
When the Instrument is in local operation the instrument is fully programmable both from
the front panel and from the bus. If a bus message arrives while a change is being entered
from the front panel, the front panel entry is interrupted and the bus message is executed.
Program and Response Messages
The communication between the system controller and the SCPI instruments connected
to the GPIB takes place through Program and Response Messages. See Figure 4B-4. A
Program Message is a sequence of one or more commands sent from the controller to an
instrument. Conversely, a Response Message is the data from the instrument to the
controller.
Controller
Program Messages
Response Messages
Device
Commands
Queries
ead103.eps
Figure 4B-4. Program and Response Messages
The GPIB controller instructs the device through program messages. The device will only
send responses when explicitly requested to do so; that is, when the controller sends a
query. Queries are recognized by the question mark at the end of the header, for example:
*IDN?
(requests the instrument to send identity data).