[A83] Re: Ion v1.6 garbled screen
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[A83] Re: Ion v1.6 garbled screen
On Wed, 12 Dec 2001, Olle Hedman wrote:
>
> At 22:49 2001-12-12, you wrote:
> >> won't it be extremely slow (assuming you're using bcall(_LCDBusy))?
>
> >Hmm, I remember reading in the SE addendum,
> >that thare's a memory address you can coll for an LCDBusy routine.
> >not quite sure though...
>
> You can read the lcd command port and check bit 7 if the lcd is busy or not.
> I'm quite sure this is what he uses.
I actually check both bit 7 (busy) and 4 (reset). I'm not sure if that is
necessary, but it works that way.
> But this too, is quite slow, since checking the value takes in avarage
> longer time then an extra long "blind" delay...
> At least it did last time I counted. I am known to have been wrong before :)
That is probably right, but it might depend on just how long "extra long"
is though. For some (though not all) 83+SE users, well over 100 cycles
between display writes seems to be needed. At least this way I have
something that I can be sure will continue to work nomatter how slow the
display controllers get in the next batch of calculators.
I am, however, quite sure that my delay is a lot faster than using any
bcall, due to the enormous overhead involved in the bcall handler.
References: