Application Specific Command Parser - Racal Instruments 7064 Instruction Manual

4.6 A P P L I C A T I O N SPECIFIC COMMAND PARSER
It is possible for the user to supply a secondary, application-specific command parser.
The 7064 has a single-threaded control flow architecture, and i t passes control to the
user's command parser under two conditions:
1. W h i l e Waiting For Input. Rather than doing a 'busy wait' on an empty input
queue, the 7064 command parser will make a function call to the user parser and
allow it to run.
Under these conditions. there may be no input for the user's parser. This
tactic affords the user's parser some extra time for computations and other
functions.
When Explicitly Directed B y The "I.TSR SCANO;" Command. T h e 7064
command parser monitors the character input stream, and parses and interprets its
own command set. W h e n the "USR_SCAN();" command is recognized in the
input stream, the 7064 command parser copies subsequent input into a secondary
queue and calls the user's parser, which is then free to fetch the characters from
the secondary queue and interpret them. I n this way, the user may freely mix
7064 and application specific command sets in the same input stream.
While running in this "user command" mode, the 7064 command parser continues to
monitor the input stream, copying characters into the secondary queue, and invoking the
user's parser until it recognizes the string "VT1_SCAN();". This string is a directive to
switch back to the normal 7064 command processing mode.
By delimiting 7064 commands and application specific commands b y the strings
"USR_SCAN();" and "VT1_SCAN();", the user is able to mix command sets in the same
input stream, and switch parsing modes at selected points.
Note that both "USR_SCAN();" and "VTl_SCAN();" should appear alone on a line,
terminated by a new line or an EOI.
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