Download logic

CSECT MASK VALUE(HEX)
OUTPUT LABEL/LOCATION/OUTPUT PRODUCED/PURPOSE
EXECUT
20
'SPIE'
just after SPIE exit label EXSPIEXT.
prints GP registers, 32 bytes of the PIE (Program
Interrrupt Element) supplied to the exit routine
by the operating system.
This is used in debugging the interpreter to make
sure that interrupts are handled properly, and are
occurring where they should.
80
'PRIMARY FETCH'
after common code to fetch next instruction and
do preliminary decoding, i.e., between labels
EXFEXENT and EXEXLEN.
prints GP registers, contents of new ECSTACKD
block for instruction just fetched, and section of
ECONTROL from ECFPREGS to ECILIMP, which shows
simulated user registers and most execution flag
flag variables.
This XSNAP essentially displays the complete
status of the simulated user machine, with the
exception of the user storage area.
40
'USER AREA'
just before label EXEXLEN, i.e., before the
instruction which has just been fetched is executed.
prints entire contents of user's simulated
storage area, with real memory addresses, which
are not normally the ones shown on the user assembly
listing.
This XSNAP is used for debugging instructions
which modify memory in any way. For instance,
this can be useful if new SVC routines or I/O
routines are added to the interpreter.