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From: grr@cbmvax.cbm.UUCP (George Robbins)
Newsgroups: comp.sys.amiga
Subject: Re: Questions on Parallel Port
Message-ID: <1741@cbmvax.cbmvax.cbm.UUCP>
Date: Sat, 25-Apr-87 16:10:51 EDT
Article-I.D.: cbmvax.1741
Posted: Sat Apr 25 16:10:51 1987
Date-Received: Sun, 26-Apr-87 21:38:40 EDT
References: <157@spycal.UUCP>
Reply-To: grr@cbmvax.UUCP (George Robbins)
Organization: Commodore Technology, West Chester, PA
Lines: 37

In article <157@spycal.UUCP> gord@spycal.UUCP (Gord Delaney) writes:
>I am attempting to connect my AMIGA to another system (an 8085/88 S100)
>via the parallel port.  After building a bi-directional parallel port
>for the S100 (from a 8255), and getting some software running on both
>sides, I have finally managed to transfer data without error in both
>directions.
>
>
>Now, to my questions:
>  - Does anyone know of a way to speed up the "par.device" driver?
>  - Is there a way that I can access the 8520 directly AND still be a
>    "well behaved task"?

	At a lower level there are various "resources" that you can reserve
	and then pound directly on the chip to you heart's content, knowing
	that other "well-behaved" tasks will be prevented from interfering
	with yo.

>                        In my hardware manual (the original CBM version),
>    in appendix E (or maybe F), a description of the 8520 is given.
>    However, very little is mentioned about the 'FLAG' and 'PC' pins.
>    Can I disable the 'FLAG' interrupt and read the status of the 'FLAG'
>    pin directly?  The 'PC' output looks like it takes care of itself.

	You should be able to do something along this line.  Of course it
	is a tradeoff - the more time you spend in buzz-loops to obtain
	the highest transfer rates, the less time available for multi-
	tasking activities...

	The I/O port and interrupt structure of the 8520 is essentially
	the same as that of the 6526 used in the C64 and C128.  Try finding
	and old MOS Technology Databook or a good C64 hardware book for
	better descriptions that the Amiga hardware manual appendix.
-- 
George Robbins - now working for,	uucp: {ihnp4|seismo|rutgers}!cbmvax!grr
but no way officially representing	arpa: cbmvax!grr@seismo.css.GOV
Commodore, Engineering Department	fone: 215-431-9255 (only by moonlite)