A86: I've got questions about registers and interupts, maby someone can
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A86: I've got questions about registers and interupts, maby someone can aswer?
What follows is a list of all the registers and the names/uses of them,
as I know them could someone please correct this list if it is wrong.
A - acender
F - flags
B - base
C - counter
D - data
E - extra
HL - 16-bit register commonly used as a mem pointer
IX - index register
IY - index register
AF' \
BC' |- shadow registers
DE' |
HL' /
R - memory refresh register (see questions about below)
I - interupt register (see questions about below)
PC - program counter
SP - stack pointer
R - What does the memory refresh register do? Is the register a count
down timer until memory refresh, then why is it a multiple of 2? Or,
does the register change after every register? And of what uses is it,
other than a pueso-random number generator (that is no good)
I - Is I the interupt vector? i.e. when an interupt occurs does the PC
now point to I? And how does that work I is only 8-bit. And what does
the interupt call do to the stack, and why do you have to return with an
RETI ($ED$4D), or do I have that wrong?
Interupt Modes
There are 3 interupt modes im 0, im 1, and im 2. Can someone tell me
the difference between the 3? I'm assuming that im 0 means no
interupts, which BTW tends to kill the calc (I think because it
disactivates (kinda) the get key routine). What are the different
interupts, I know the clock (200Hz) and the ON key, any one know of any
others?
Also, I have been thinking about getting the processor into a state
where the ROM has no influence what so ever. I think I can do it by
starting a program that removes all the interupts and than I can have
that same program recive a transver through the link port to fill the
rest of the ram with code. Just an idea.
-Gen_Witt
Gen_Witt@aloradus.com
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