gfa code timer speed

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charles
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gfa code timer speed

Postby charles » Tue Oct 17, 2006 12:59 am

hello and much thanks too all
now i am addressing the atari's timer speed.

has anybody a glimpse of hope towards a gfa approach at variating the speed of the timer?

i do but it seems quite "grizzly" ,acheiving "uncontrolable madness"
at the moment

1 makes real slow ,2 makes fast 4 and 5 are dumb , any of the numbers i poke just seem to have no real presidence over the next ,
no real asending/descending order....all have some affect but most just remain vague.

i kind of figure it would be good for a demo that needs a fast forward button for slow spots , you know..
i'll post my code for the poke of the vector but its realling just a "kiddie"attempt to simulate the real harness.

thank you
callaghan
The radioactive half-life : )
Atari is a lifestyle,not a hobby.
HOLD ON ! ! ! Im printing unreadable characters ...!

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daeghnao
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Postby daeghnao » Tue Oct 17, 2006 9:30 am

Obviously, you need to locate, read and understand some comprehensive documentation for the 68901 chip that you're trying to program. However, I couldn't find this documentation online when I just looked. Does anyone know where to get this information? I have some in "St Internals" but that's not very online.

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charles
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timer speed

Postby charles » Tue Oct 17, 2006 10:27 am

i too have a copy of st internals .
what little knowledge i have of computer terms is all jumbled up due to
lack of professional training.
myself i have approx fiftey or sixtey atari programming books,the trouble is referencing them all , finding what i need , making sence of it , applying the jargon , then ultimitly referencing it agaist what someone here at the forum has to say .......
so you feel there isn't suffiecent documentation in the st internals?
me too!!!
they need to break down all addresses with examples,if the're going to succesfully demonstrate how to program the st.
thanx
callaghan

on line resources coming up ,gotta go to work then going to post what i have found for "tools"
The radioactive half-life : )
Atari is a lifestyle,not a hobby.
HOLD ON ! ! ! Im printing unreadable characters ...!

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daeghnao
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Re: timer speed

Postby daeghnao » Tue Oct 17, 2006 1:30 pm

callaghan wrote:i too have a copy of st internals .
what little knowledge i have of computer terms is all jumbled up due to
lack of professional training.
myself i have approx fiftey or sixtey atari programming books,the trouble is referencing them all , finding what i need , making sence of it , applying the jargon , then ultimitly referencing it agaist what someone here at the forum has to say .......


It's a steep learning curve, but it's quite rewarding to achieve something.

so you feel there isn't suffiecent documentation in the st internals?


Actually, I think ST Internals, although it has a few errors in it, is a very good all-round reference. I managed to write my own replacement keyboard interrupt handler from it, a long time ago (still intend to revamp that with modern programming practices).

me too!!!
they need to break down all addresses with examples,if the're going to succesfully demonstrate how to program the st.


I suspect that would be a much larger book. I don't have any docs to hand, but I seem to recall that timers C and D are both controlled with different halves of a single control register "TCDCR", plus there'll be a count register for timer C, and the default settings will be something like control = divide by 64, counter = 192 to get down to 200Hz from the... er... 2.4576MHz clock, I think it is. Well, the numbers work out OK on my calculator :)

I can't remember offhand the mapping from bits in the control register to divider ratios, but it's in ST Internals - look for the definitions of TACR, TBCR, TCDCR. The control registers are OK for reading and writing, but the count register, I think, gives the current value of the countdown rather than the value it resets to each time, so you have to know what it was set to to begin with. There are some XBIOS calls that help to set up timers, too.

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charles
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wow!

Postby charles » Tue Oct 17, 2006 11:55 pm

hello daeghneo
wow you make a world of difference..
your great!
thanks , my practises are not in the computer field, i build houses with a builder for a living, computers are onl;y my hobby..]

well in any case i'll release my findings as soon as uncovered.
so how old are you?
do have you a main profession which ulitlizes computers ?
yoiu're so smart!

ok bye too many q's for now
callaghan
pm me if too personal
The radioactive half-life : )
Atari is a lifestyle,not a hobby.
HOLD ON ! ! ! Im printing unreadable characters ...!


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