[A83] LCD update freq and working with 16bit numbers on the Z80
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[A83] LCD update freq and working with 16bit numbers on the Z80
I'm just starting out programming TI83 assembly. I have programmed some
8-bit assembler (6502/6510, the good old C64!) like 10 years ago, but I've
no experience when it comes to Z80.
Anyway, I'm mainly doing graphical (demo style) effects at the moment, and I
often have the need to add and subtract a 16 bit reg (hl) that I have
pointing somewhere in the PLOTSSCREEN by 12 (one row).
Adding by 12 is easy, since there is a 16 bit add, but subtracting by 12
seems to be very complicated, the only solution I could have come up with
this far is this (which looks like it's waisting many clock cycles) :
ld a,l
sub 12
ld l,a
ld a,h
sbc a,0
ld h,a
I guess I'm overlooking something, or is this the best way to do it?
My second question - does anyone know how many times per second you can
update the LCD using the _GRBUFCPY_V call? I mean, what 'FPS' is the
theoretical max, assuming that nothing else but the buffer copy is done?
/Andreas
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