Re: A83:STILL NEED HELP!

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Re: A83:STILL NEED HELP!


What the routine is doing is that it is using the busy flag to check whether
the last operation has been completed. To use this flag you have to do a
read first, so you can not just connect it to a pin on the Z80. So it is not
costs which stoped TI from doing it.

If you include the function as a macro then delay will be 11+x*25 T states
so the delay would probably end up being 61 T states which is 1 T states
longer than the delay TI uses. So wouldn't a better solution be to use TI's
delay routine, it is faster, smaller and garenteed to work.
(in 11 T, rla 4, jp 10)

If you are writing your own graphics routines I would recommend not doing
this unless you do not care about speed since a lot of time is wasted. As an
example the display routiens in CrASH uses a delay of 12 T states, the rest
of the time is spend on doing useful stuff.

DInes

From: Laurens Holst <laurensh1@yahoo.com>
To: <assembly-83@lists.ticalc.org>
Sent: 25. oktober 1999 13:23
Subject: Re: A83:STILL NEED HELP!


>
> > Why not just keep reading the port until it's ready?  My wait routine
> > looks like this:
> >
> > dWait:  in a,(10h)
> >         rla
> >         jr c,dWait
> >         ret
> >
> > Is that inefficient?
>
> Whaa??? Is that possible??? Didn't know about that... Anyways, that's
great!
> I'll put this in my routines I think, then I'll be sure it's 83+
> compatible...
>
> About the inefficiency, yes it is indeed a bit inefficient. But a pro is
> that it will ALWAYS work. It just depends on how fast you need the
> 'fastCopy' routine to be. Actually, this bit should be connected in some
way
> with the WAIT pin of the Z80 so that as soon as an OUT is done to ports
#10
> or #11 and this bit is not reset yet the Z80 will wait until it's ready.
But
> well, anyways, Texas Instruments decided not to do this... Cuts back on
> costs but I think it's too bad they didn't do this...
>
> Oh, and by the way, using a JP instead of a JR increases the reaction
> time... But it doesn't differ much, and it takes 2 bytes more space... The
> choice is yours.
>
>
> ~Grauw
>
>
> --
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>
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