Programmer’s Guide 1-15
Introduction to GPIB Programming
Programming Fundamentals
Output Queue
The output queue temporarily stores a single response message until it is
read by a controller. It is cleared when the following actions occur:
• the message is read by a controller
• the analyzer is turned on
• the Device Clear (DCL) or Selected Device Clear (SDC) command is
received
Command Parser
The command parser reads program messages from the input queue in
the order they were received from the bus. It analyzes the messages to
determine what actions the analyzer should take.
One of the parser's most important functions is to determine the position
of a program message in the analyzer's command tree (described in
Chapter 9). When the command parser is reset, the next command it
receives is expected to arise from the base of the analyzer's command
tree.
The parser is reset when the following actions occur:
• the analyzer is turned on
• The Device Clear (DCL) or Selected Device Clear (SDC) command is
received.
• a colon immediately follows a semicolon in a program message. (For
more information see “Sending Multiple Commands” on page 9-7.)
• A program message terminator is received. A program message
terminator can be an ASCII carriage return (
C
R
) or newline character
or the GPIB END message (EOI set true).
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