4 Nov
2000
4 Nov
'00
11:22 a.m.
I wrote:
And both the Z-80 and 6502 have at least one more
bit that's "sort of" programmer visible, the NMI
edge-detect flop.
Allison wrote:
I tried to limit it to the programmer accessable. If
we add temp registers and whole knows what in the
state or microcode portion of the machine it surely
would grow more.
I'm not including internal temporaries that are not
exposed in any way either. But depending on how your
hardware is wired, the NMI edge detect flop can have
substantial influence on how you write your interrupt
handler. Thus it is in fact programmer visible, though
not as much as e.g. the Z-80's R register.