Fluke 5820A, Руководство оператора

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5820A
Operators Manual
5-28
5-24. Types of Commands
The commands for the 5820A Calibrator can be grouped into one or more categories,
depending on how they function. Each category is described below.
5-25. Device
−
Dependent Commands
Device-dependent commands are unique to the 5820A Calibrator. An example of a
device-dependent command is,
SCOPE MARKER
instructing the 5820A Calibrator to the TIME MARKER function.
5-26. Common Commands
Common commands are defined by the IEEE 488.2 standard and are common to most
bus devices. Common commands always begin with an * character. Common commands
are available whether you are using the IEEE-488 or RS-232 interface for remote control.
An example of a common command is,
*IDN?
instructing the 5820A Calibrator to return the instrument identification string.
5-27. Query Commands
Query commands request information, which is returned as the command executes, or
placed in a buffer until requested. An example of a query, which always ends with a
question mark, is,
SCOPE?
inquiring about the 5820A mode of operation.
5-28. Interface Messages (IEEE-488)
Interface messages manage traffic on the IEEE-488 interface bus. Device addressing and
clearing, data handshaking, and commands to place status bytes on the bus are all
directed by interface messages. Some of the interface messages occur as state transitions
of dedicated control lines. The rest of the interface messages are sent over the data lines
with the ATN signal true. (All device-dependent and common commands are sent over
the data lines with the ATN signal false.)
An important thing to note 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 5820A Calibrator, the
controller automatically sends the interface message MTA (My Talk Address).
IEEE-488 standards define interface messages. Table 5-5 lists the interface messages that
the 5820A Calibrator accepts. Table 5-5 also shows the BASIC statement to generate the
interface message. Table 5-6 lists the interface messages that the calibrator sends. The
mnemonics listed in the tables are not sent in BASIC PRINT statements as commands
are; in this way they are different from device-dependent and common commands.
Interface messages are handled automatically in most cases. For example, handshake
messages DAV, DAC, and RFD automatically occur under the direction of an
instrument's interface itself as each byte is sent over the bus.