Re: TI-H: asm

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Re: TI-H: asm


S43R80 wrote:

> ok...i am trying my best to learn how to program in assembly using
> zshell...right now i am a little stuck though...will someone please explain to
> me how and why these routines (from the zshell school) actually work (word for
> word).
>
> PLOTTING PIXELS
>
> Here are four routines for putting a pixel, removing a pixel, changing a
> pixel, and checking to see if a pixel is lit.
>
>      PutPixel: ; Puts a pixel at B,C
>       ROM_CALL(FIND_PIXEL)
>       ld de,$FC00
>       add hl,de
>       or (hl)
>       ld (hl),a
>       ret
>
>      RemovePixel: ; Removes a pixel at B,C
>       ROM_CALL(FIND_PIXEL)
>       ld de,$FC00
>       add hl,de
>       cpl
>       and (hl)
>       ld (hl),a
>       ret
>
>      ChangePixel: ; Changes the pixel at B,C
>       ROM_CALL(FIND_PIXEL)
>       ld de,$FC00
>       add hl,de
>       xor (hl)
>       ld (hl),a
>       ret
>
>      TestPixel: ; Tests the pixel at B,C. If the Z flag is set, no pixel, else
> a pixel is lit
>       ROM_CALL(FIND_PIXEL)
>       ld de,$FC00
>       add hl,de
>       and (hl)
>       ret

You should ask that on the Assembly-85 mailing list, not this list.

--
Bryan Rabeler <brabeler@ticalc.org>
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