Fluke PM6685, PM6681R Program and Response Messages, Syntax and Style, Syntax of Program Messages

		Introduction to SCPI
Program and Response Messages
The communication between the system	One or more program message units
controller and the SCPI instruments con-	(commands) may be sent within a simple
nected to the GPIB takes place through	program message, see Fig. 3-6.
Program and Response Messages. A Pro-
gram Message is a sequence of one or		;
more commands sent from the controller
to an instrument. Conversely, a Response	< P r o g r a m M e s s a g e U n it >
Message is the data from the instrument
to the controller.	Fig 3-6	Syntax of a terminated
		Program Message.

C o n t r o l l e r					D e v i c e
			C o m m a n d s
	P r o g r a m M e s s a g e s				￿ is the pmt (program message
				The
			Q u e r i e s
				terminator) and it must be one of the fol-
	R eposn s ege	Ms e s s a
				lowing codes:

Figure 3-4Program 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 con- troller sends a query. Queries are recog- nized by the question mark at the end of the header, for example: *IDN? (requests the instrument to send identity data).

Syntax and Style

￿Syntax of Program Messages

A command or query is called a program message unit. A program message unit consists of a header followed by one or more parameters, as shown in Figure 3-5 .

￿	NL^END	This is <new line>
		code sent concur-
		rently with the
		END message on
		the GPIB.
	NL	This is the <new
		line> code.
	<dab>^END	This is the END
		message sent
		concurrently with
		the last data byte
		<dab>.

￿NL is the same as the ASCII LF (<line feed> = ASCII 10decimal ). The END message is sent via the EOI-line of the GPIB.

The ^ character stands for ‘at the same time as’.

,

< H e a < S p>a c< eP >a r a m e t e r >

Figure 3-5Syntax of a Program

Message Unit.

Program and Response Messages 3-7