A82: Re: Re: display port vs. graph_mem


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A82: Re: Re: display port vs. graph_mem




The display controller needs a certain amount if time to finih the
operation. The TI routine is just too long a delay.  The best way to
implement the delay is by using the time to do something which needs to be
done anyway. IF there is not enough stuff to do while you wait include some
instruction which does not destroy any of the register untill the delay is
long enough.

Another possibility is to read the status byte and check that the busy bit
is not set, it takes up more space an is a bit slower than the above method,
but it is the "correct" way of doing it (and it is faster than the TI way,
but always works).

DInes
/----------------------------\
| Dines Justsen              |
| dines@aub.dk               |
| www.student.dtu.dk/~c958362|
\----------------------------/

----- Original Message -----
From: "Doug Torrance" <profzoom@hotmail.com>
To: <assembly-82@lists.ticalc.org>
Sent: Monday, January 24, 2000 3:17 AM
Subject: A82: Re: display port vs. graph_mem


>
>
> What's the purpose of the delay routine?  Does the display port just need
> some time to function?  I know this is TI's routine:
>
> push    af
> inc     hl
> dec     hl
> pop     af
> ret
>
> What's a better one?
>
> Thanks,
> Doug
>
>
> >The only way to access the display is by using the ports to write each of
> >the bytes to display, so using the display controller directly should be
> >faster. The CR_GRBCopy is very optimized, so to increse speed by writing
> >directly to the port you need to use optimized routines too.
> >
> >The advantage of using CR_GRBCopy is that one can use block copy to
output
> >the bitmap to the LCD, which combined with writing column by column
speeds
> >up the process.
> >
> >If trying to use the display controller directly remember the following:
> >- - Do not use the TI delay, it is way to long
> >- - Use block copy to write sprites etc
> >- - For most sprites write column by column
> >
>
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>



References: