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From: sl122057@silver.bacs.indiana.edu
Newsgroups: comp.sys.amiga
Subject: Re: Amiga midi problems?
Message-ID: <18700010@silver>
Date: Fri, 7-Aug-87 19:59:00 EDT
Article-I.D.: silver.18700010
Posted: Fri Aug  7 19:59:00 1987
Date-Received: Sun, 9-Aug-87 08:17:34 EDT
References: <1408@ico.UUCP>
Organization: Indiana University BACS, Bloomington
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Nf-From: silver.bacs.indiana.edu!sl122057    Aug  7 18:59:00 1987


Can someone explain the details of the serial port and timers, then?  The
manuals aren't real clear about exactly what is going on in there.
Specifically:
  
  1.  What is the exact relationship between the 8520's, Paula, and the port
	  on the back?  Section 8.6 in the hardware manual seems to imply that
	  you can use the port without messing with the 8520, but then Appendix
	  F seems to say that this is where the work is really done.  So is the
	  port connected to both chips, or is one just lower level than the other?

  2.  If you want to use the serial port, do you need to allocate the 8520A
	  timer A so no other task will grab it?

  3.  Exactly how do you allocate some part of an 8520?  The cia.resources
	  let you allocate the interrupts, etc., but not the bits themselves.
	  So do we just use the interrupt allocation scheme to insure mutual
	  exclusion, even though we may not be actually using the interrupt?

  4.  For MIDI purposes, one of the TOD clocks would probably be more useful
	  than one of the interval timers.  Is one of these clocks free for 
	  application programs, and if so, does it count color clocks?  If so,
	  Time Of Day seems like a misnomer, since that would only give you
	  a maximum time interval of aobut 5 seconds.  Am I missing something?
	  How is the system time maintained?  The RKM says something about using
	  the line frequency.

Sorry about the length, and I hope I haven't wasted anyone's time by
asking obvious questions.