Programmer’s Guide 1-13
Introduction to GPIB Programming
Programming Fundamentals
When the status byte is returned in response to a serial poll, bit 6 acts as
the Request Service (RQS) bit. If the bit is set, it will be cleared after the
status byte is returned.
The Serial Poll Disable (SPD) command causes the analyzer to leave the
serial poll mode.
Take Control Talker (TCT)
If the analyzer is addressed to talk, this command causes it to take
control of the GPIB. It becomes the active controller on the bus. The
analyzer automatically passes control back when it completes the
operation that required it to take control. Control is passed back to the
address specified by the *PCB command (which should be sent prior to
passing control).
If the analyzer does not require control when this command is received,
it immediately passes control back.
Message Exchange
The analyzer communicates with the controller and other devices on the
GPIB using program messages and response messages. Program
messages are used to send commands, queries, and data to the analyzer.
Response messages are used to return data from the analyzer. The
syntax for both kinds of messages is discussed in Chapter 9,
“Introduction to SCPI.”
There are two important things to remember about the message
exchanges between the analyzer and other devices on the bus:
• The analyzer only talks after it receives a terminated query (see
“Query Response Generation” on page 1-16).
• Once it receives a terminated query, the analyzer expects to talk
before it is told to do something else.
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