User`s guide

2-9

Programming Getting Started

Receiving Information from the Instrument

After receiving a query (command header followed by a question mark), the

instrument interrogates the requested function and places the answer in its

output queue. The answer remains in the output queue until it is read or another

command is issued. When read, the answer is transmitted across the interface

to the designated listener (typically a controller). The input statement for

receiving a response message from an instrument’s output queue typically has

two parameters; the device address, and a format specification for handling the

response message. For example, to read the result of the query command

:CHANNEL1:COUPLING? you would execute the HP BASIC statement:

ENTER <device address> ;Setting$

where <device address> represents the address of your device. This would

enter the current setting for the channel one coupling in the string variable

Setting$.

All results for queries sent in a program message must be read before another

program message is sent. For example, when you send the query

:MEASURE:RISETIME?, you must follow that query with an input statement.

In HP BASIC, this is usually done with an ENTER statement.

Sending another command before reading the result of the query clears the

output buffer and the current response. This also causes an error to be placed

in the error queue.

Executing an input statement before sending a query causes the controller to

wait indefinitely.

The format specification for handling response messages is dependent on both

the controller and the programming language.