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

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





>From: "Ronald Teune" <rtwolf@gmx.net>
>Reply-To: assembly-83@lists.ticalc.org
>To: "Assembly 83" <assembly-83@lists.ticalc.org>
>Subject: [A83] Official H**s Replacement Commands & Questions & 
>PulseWidthModulation
>Date: Mon, 2 Jul 2001 14:38:53 +0200
>
>
>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...

Wow... Those commands are pretty crappy. :)

Actually, the only real h**s replacement command is changing the .db line 
that contains the game's title, then changing the .db line containing the 
author.

>
>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?)

It replaces (de) with (hl), then decreases bc.  Then it does it again and 
again until bc = 0.  This copies chunks of memory, also can be used to set 
memory ranges to a single value.


>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?

bit 0, = first bit
bit 7, = last bit.

bit supports single registers and (hl)/(ix)/(iy). (ix and iy of course have 
offsets)
It returns the zero flag for 0, and nz for 1.

set turns a bit on, res turns a bit off.  Bits are arranged from right to 
left:

     76543210
.db %........

>
>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

If b=0 then it waits 256 times, not 0.  Also, B is getting reset to 0 by the 
djnz.  Use this instead:

Wait:   ei \ push bc
WaitLoop:   halt \ djnz waitloop \ pop bc \ ret

Also, I think halt is a poor choice for sound here, you will end up with 
lower pitches.  use a subloop involving nops or something faster.
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