12-14-2021, 12:33 AM
Edited to correct title.
I'm trying to make sense of the various processor flags and status bits used by the HP67,
I'm reasonably happy with what the flags do though there are a couple of gaps in the table, and I can't work out if the mode flag should be set directly from the switch position.
However I'm rather less clear on which status bits are set or cleared directly by the hardware. S15 is set when any key is pressed and S11 appears to be set by the RUN/PRGM switch position.
However I'm unsure if any other bits are set or cleared directly by the hardware or what effect the CRC instructions have on them.
Thank you.
I'm trying to make sense of the various processor flags and status bits used by the HP67,
I'm reasonably happy with what the flags do though there are a couple of gaps in the table, and I can't work out if the mode flag should be set directly from the switch position.
Code:
Processor flags - 10 processor flags ? (F 0 - F 9)
F 0 #? Run / Program mode
F 1 Carry
F 2 Prev Carry
F 3 Delayed ROM select
F 4 ROM select
F 5 Display enabled
F 6 ???
F 7 ???
F 8 Timer (Not used)
F 9 ???However I'm rather less clear on which status bits are set or cleared directly by the hardware. S15 is set when any key is pressed and S11 appears to be set by the RUN/PRGM switch position.
However I'm unsure if any other bits are set or cleared directly by the hardware or what effect the CRC instructions have on them.
Code:
Processor status word - 16 status bits (S 0 - S 15)
# set/cleared by hardware?
S 0 unused ?
S 1 unused ?
S 2 unused ?
S 3 run/prgm mode? (set from switch position by CRC 300 cleared by CRC 1500?)
S 4 used ?
S 5 # power OK ?
S 6 used ?
S 7 ?
S 8 used ?
S 9 ?
S 10 ?
S 11 ? (not the PRGM/RUN switch state!)
S 12 (logical not) stack lift ?
S 13 function key pressed
S 14 ?
S 15 # set if any key is pressedThank you.