[A83] Re: Official H**s Replacement Commands & Questions & PulseWidthMod

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[A83] Re: Official H**s Replacement Commands & Questions & PulseWidthModulation


LDIR copies BC bytes from HL (source) to DE (dest). It's not very efficient,
though. Unrolling it as LDI's is more efficient.

Bits are 7,6,5,4,3,2,1,0 in that order: so using the bit command tests that
bit of the byte. Sensibly, if the bit is nonzero (1), then you check that
with the NZ flag..

It doesn't exactly seem that your code would work, because B is always reset
to the value 0 after one go through the loop, which would make changing the
width not be noticed. But optimization ideas anyway:

#define WAIT ei\ halt\ djnz $-2
begin:
    ld b,0
loop:
    bcall(_getky)
    cp kDown
    inc b \ ret
    jr nz,notdown
notdown:
    cp kUp
    jr nz,notup
    dec b \ ret
notup:
    cp kClear
    ret z
    ld a,$C3    ;off
    out($00),a
    WAIT
    ld a,$C0    ;on
    WAIT
    jr loop

-----Original Message-----
From: assembly-83-bounce@lists.ticalc.org
[mailto:assembly-83-bounce@lists.ticalc.org]On Behalf Of Ronald Teune
Sent: Monday, July 02, 2001 6:39 AM
To: Assembly 83
Subject: [A83] Official H**s Replacement Commands & Questions &
PulseWidthModulation



HRC1: ex de,hl = push de \ push hl \ pop de \ pop hl ;this should work, I
guess
HRC2: ld a,xx = push bc \ ld b,xx \ ld a,b \ pop bc
More crap coming soon, maybe...
Feel free to add other commands...

Question:
1 What does ldir do? Does it copy the graph buffer to the screen? In
   ionm.z80 it's used to run a module stored in saferam1 (graph buffer?)
2 Is there a command that extracts bits from a variable? I think 'bit' does
   the trick, so bit 1 is the first bit of a and bit 2 is the 2nd bit of a
   and bit 3 the 3rd, ... and I think it sets the zero flag for 1 and the
   nonzero flag for 0. Is this correct?

PWM:

Didn't test it, but this should work. The 'on' pulse is a bit longer than
the 'off' pulse.

begin:
    ld b,0
loop:
    bcall(_getky)
    cp kDown
    call z, incb    ;speed down
    cp kUp
    call z, decb    ;speed up
    cp kClear
    ret z
    ld a,C3    ;off
    out(00),a
    call wait
    ld a,C0    ;on
    call wait
    jp loop
incb:
    inc b \ ret
decb:
    dec b \ ret
wait:
    ei \ halt \ djnz wait \ ret
References: