Re: A85: line
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Re: A85: line
On Sun, 3 May 1998 11:00:51 -0500, you wrote:
>
>>Use the FLINE funtion that comes with Usgard1.5.
>
>there's an easier way to make horizontal lines like this:
>
he said he wanted a diagonal line though, which isn't much more
difficult. you just need to use a register to act as a bit mask and
shift it left or right. a bit mask has only one bit set to 1, such as
$80, $40, $20, $10, $08, .... all you need to do is "OR" this value
with the value in the video memory then rotate it left or right and
move up or down in video memory (16 bytes). then if a carry out
occurs, after rotating left with $80 or right with $01, you would need
to either add one less byte (15 bytes) or one more byte (17 bytes).
-mike pearce
References: