Fluke 5502A, Руководство оператора

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5502A
Operators Manual
5-28
Query Commands
Query commands request information. That information is given as the command
executes, or the information is put into a buffer until requested. An example of a query,
which always completes with a question mark, is,
RANGE?
This shows the Calibrator primary and secondary outputs.
Interface Messages (IEEE-488)
Interface messages manage traffic on the IEEE-488 interface bus. Device addressing and
clearing, data handshaking, and commands to put status bytes on the bus are all directed
by interface messages. Some of the interface messages occur as condition changes of
dedicated control lines. The remaining interface messages are sent with the data lines
with the ATN signal true.
Note
All device-dependent and common commands are sent over the data lines
with the ATN signal false.
An important thing about interface messages is that unlike device-dependent and
common commands, interface messages are not sent literally (in a direct way). For
example, when you send a device-dependent query to the Calibrator, the controller
automatically sends the interface message MTA (My Talk Address).
IEEE-488 standards define interface messages. Table 5-4 shows the interface messages
that the Calibrator accepts. Table 5-4 also shows the BASIC statement to make the
interface message. Table 5-5 shows the interface messages that the Calibrator sends. The
mnemonics shown in the tables are not sent in BASIC PRINT statements as commands
are; this is how they are different from device-dependent and common commands.
Interface messages are controlled automatically in most cases. For example, handshake
messages DAV, DAC, and RFD automatically occur with the direction of an interface of
the instrument as each byte is sent over the bus.