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The EXEC option traces the execution of instructions that match user-specified criteria. When a match occurs, all
CPU trace options are turned on for the duration of the execution of the matched instruction. The prior trace
settings are restored when a match fails. This option allows detailed tracing of specified instructions while
minimizing the log file size compared to a full instruction trace.
The SET CPU EXEC command configures the match and mask values used to qualify instructions for execution
tracing. Qualification is performed by ANDing the current instruction with the specified mask value and then
comparing the result with the specified match value. If the mask value is omitted, the match value must match the
instruction exactly. The values are entered in the CPU’s data radix, which defaults to octal but may be set to a
different radix or overridden by a switch on the command line.
Setting the mask value allows matching a range of instructions or an instruction with a range of operand values.
For example, SET CPU EXEC=105240;177760 will trace execution of all EMA or VMA firmware instructions, SET
CPU EXEC=102700;177700 will trace execution of STC instructions, and SET CPU EXEC=105040 will trace
execution of FMP instructions.
If idling has been enabled with the SET CPU IDLE command, tracing will be suspended when the simulator detects
an entry into the operating system idle loop. This is done to avoid printing the hundreds or thousands of loop
instructions that are executed while awaiting an interrupt. Tracing is automatically resumed when the idle loop is
exited either by an interrupt or a simulation stop.
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