Re: A86: 3-color icons?


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Re: A86: 3-color icons?



At 12:15 PM 9/7/97 -0400, you wrote:
>In a message dated 97-09-05 22:33:24 EDT, you write:
>
><< No, it can only support black and white.  What you saw as grey when your
> calculator crashed was the result of rapidly-changing data in the vido
> buffer. >>
>
>when it crashed and locked up there were about six or more (yes, six)
>different shades of grey including black and white.  if they were spread all
>over the graph screen, how is it that the video buffer could change all of
>those so rapidly?
>
>

you can change the offset of the video memory by sending a value through a
port.  It's originally set to $FC00, like normal.  But if you change the
value, it switches _very_ quickly to another screen, and then to another,
then back, then do the process again.  That's the quickest way to do
grayscale.

You can also use the ldir command, like so:

	ld hl,$C000	;look at stuff from this place in memory
	ld de,$FC00
	ld bc,$0400
	ldir		;new screen loaded that quickly

This is how all 4 and 8 grayscale programs work, usually the port switching
is done in interrupts.  Believe it or not, it can switch it fast enough to
be flicker-free grayscale.


-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
 Alan Bailey            mailto:bailela@charlie.cns.iit.edu
 IRC:Abalone              Web:http://www.iit.edu/~bailela/
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
 


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