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24.1. Calling Sequence
There are two formats available for calling SNOOPY.
Format 1
SLJ SNOOPY$
+ mode-bits,termination-addr . mode-word
where:
mode-bits (bits 0 through 17 where bit 0 is the leftmost bit)
Program Trace Routine
Bit 17 controls quarter-word mode sensitivity. If bit 17 of the mode word is set,
SNOOPY simulates quarter-word mode for checkout of quarter-word sensitive
programs on machines without quarter-word hardware. If bit 17 is clear,
SNOOPY uses either third- or quarter-word mode, depending on the mode set in
the Processor State Register (PSR) on entry. If bit 18 is set, the mode word
suppresses the solicitation of commands at the beginning and end of a trace
when using SNOOPY in demand mode.
termination-addr (bits 18 through 35)
Format 2
Tracing begins with the instruction following the mode word. Tracing continues
until the termination address (termination-addr) is reached or until another
termination condition is encountered.
SLJ TON$
Tracing begins following the SLJ instruction and continues until it encounters a
termination condition. The quarter-word mode sensitivity is unchanged with this
format.
24.2. Terminating Trace
Tracing is terminated in batch mode by any of the following:
• Reaching the specified termination address. Program execution continues.
• Using the SLJ TOFF$ instruction (program execution continues). If an SLJ TOFF$
instruction is executed outside of the trace routine, it has no effect.
• Using the ER EXIT$ instruction (see the Exec ER Programming Reference Manual).
This not only terminates SNOOPY, but it also terminates the activity being traced.
• Encountering a program contingency of types 1, 2, 7, or 12 for which standard
system action has been specified. The activity being traced is terminated by EXIT$.
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