Re: A86: Re: FindPixel

To: <assembly-86@lists.ticalc.org>
Subject: Re: A86: Re: FindPixel
From: "Matt2000" <matt2000@gte.net>
Date: Tue, 5 May 1998 20:56:00 -0400
Delivered-To: assembly-86-outgoing@towerguard.unix.edu.sollentuna.se
Reply-To: assembly-86@lists.ticalc.org


>        ld hl,FP_Bits   ; HL -> bitmask table
>        ld a,e          ; A = x coordinate
>        and $07         ; A = bit offset
>        or a,l          ; add bit offset to HL (the addition to L will
>        ld l,a          ;  not carry, because the table is aligned)
>        ld c,(hl)       ; C = bitmask (saved for later)


.org (($+8) & 0FFF8h)   ; align FP_Bits on the next 8-byte boundary

Ok I understand tell me if this is correct

1.) The address is cleared of the last 3-bits but adds 8 bytes since
clearing the last 3-bits could of subtracted up to 8 bytes from the address.

2.) Since the last 3-bits of the FP_Bits address is clear, you can easily
add 3-bits (0-7) and there is no chance of the carry flag being set. Clever
clever

-Matt

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Re: A86: Re: FindPixel

From: Dan Eble <eble@cis.ohio-state.edu>

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