Messages   

The messages transferred on the data lines of the GPIB bus or via the RSIB interface can be either interface messages or device messages.

GPIB Bus Interface Messages

Interface messages are transferred on the data lines of the GPIB bus, the ATN control line being active. They are used for communication between controller and instrument and can only be sent by a computer which has the function of an GPIB bus controller.

Interface messages can be further subdivided into

• Universal commands act on all devices connected to the GPIB bus without previous addressing.

• Addressed commands only act on devices previously addressed as listeners.

The interface messages relevant to the instrument are listed in the GPIB bus section.

RSIB Interface Messages

The RSIB interface allows the instrument to be controlled in a Local Area Network. The interface functions are matched to the function interface for GPIB bus programming from National Instruments.

Device Messages (Commands and Device Responses)

Device messages are transferred via the data lines of the GPIB bus, the "ATN" control line not being active. The ASCII character set is used. A distinction is made according to the direction in which device messages are transferred:

• Commands are messages the controller sends to the instrument. They operate the device functions and request information.

• Device responses are messages the instrument sends to the controller after a query. They can contain measurement results, instrument settings and information on the instrument status.

Commands are subdivided according to two criteria:

1. According to the effect they have on the instrument:

• Setting commands cause instrument settings such as a reset of the instrument or setting the output level to some value.

• Queries cause data to be provided for output on the GPIB bus, e.g. for identification of the device or polling the active input.

2. According to their definition in standard IEEE 488.2:

• Common commands have a function and syntax that is exactly defined in standard IEEE 488.2. Typical tasks are the management of the standardized status registers, reset and selftest.

• Device-specific commands are functions that depend on the features of the instrument such as frequency settings. A majority of these commands has also been standardized by the SCPI consortium.

The device messages have a characteristic structure and syntax. In the SCPI reference chapter all commands are listed and explained in detail.