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| From: Crown (all posts)
Date: 1998-06-01
Subject: Re: New questions...
|
Hi there,
>Okay, I have some new ones to ponder.. :-)
Sure, they are always welcome :))
>1) Does the DMA delay change in Bitmap mode, or since it still fetches
>from both charscreens, does it remain constant.. (an easy one to start
>with) :-)
It has to fetch the same amount of bytes, so it remains the same.
Bitmap mode is only different from char mode in two ways. First the interpretation of the screen attribute bytes differ ($0800, & $0c00),
and the address generation for the bitmap differs. It's possible,
that $ff1a-$ff1b is used in generating these addresses.
>2) Can someone do a table of volume translations from the plus 4
>digiconvertor values into a zero to one value. This would help LOADS!
>
If bit 7 is set: (if it's not set that means normal ops)
x = low nybble (bit 0..3)
mul = 0 if both bit 4 and bit 5 is not set mul = 1 if either bit 4 or bit 5 is set mul = 2 if both bit 4 and bit 5 is set alg:
if (x>8) x=8;
value = mul*x/16;
>3) What is the FIRST "FF1E" value on a new scan line, that is from
>when the TED table starts.. i.e.
>
>FastModeDMA
>pppp-*-*-*-SFSFSFSFSF... etc.
>
>What is the value at the first "p" - I "think" it should be "$D0"..
>but Im not sure..
It is $C4.
I do hope, this was clear. :)
Tibor Biczo / Crown of GOTU
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