Path: utzoo!utgpu!water!watmath!clyde!att!ucbvax!UICVM.BITNET!U46050
From: U46050@UICVM.BITNET (JOHN ZAFIRIS)
Newsgroups: comp.sys.atari.st
Subject: interrupts
Message-ID: <8810200352.AA14925@ucbvax.Berkeley.EDU>
Date: 20 Oct 88 03:55:12 GMT
Sender: usenet@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 40

Mike Russell writes the following in response to my "interrupts" note:

>        1) turn of timer C - this gets rid of most of the big interrupts
>                and largely solved my problem of doing programmed i/o to
>                get a video image.
>
This looks promising: I'll give it a try.

>        4) set the processor level to 7.  This shuts out everything, however
>                keyboard event processing can easily get out
>                of synch if you leave things like this for more than 3ms.
>                Not a pretty sight - the keyboard decides it received a key
>                down event  - then auto repeat kicks in.  Yuck.

The keyboard getting out of sync might be what is causing my trouble
but would it do so much as freeze the machine up?  I could see how the
keyboard could get messed up and repeat 'til the cows come home but this
(I don't think) would cause the machine to freeze up.  My routine leaves
interrupts off for much longer than 3ms.  Is there a way to get around
this?

>I can send you this code if you think it'd be useful.   It compiles under
>Laser C.  It's a bit of trouble for me to send it, so please consider
>how useful it will be to you.
>
>Other questions: are you doing any disk i/o?  If so losing interrupts could
>hang things.  Are you doing the spl's from interrupt code?  Any bios, xbios,
>vdi, or aes calls with the priority set high?  Any details on exactly what
>you're trying to do will help.  If you just need reasonably quick access
>to an ST device there may be some tricks you can do with interrupts.

I haven't done anything in C for years and would have more trouble
understanding the language than the algorithm...thanks for the offer.

The ONLY part of the ST that I use is the ports on the sound chip (A & B).  I
use them to transfer data to another computer using a custom (read: rigged)
parallel port and one handshaking line.  The handshaking timing is what is
critical.

Thanks for the suggestions.  I'll look into them...             ...John