Path: utzoo!attcan!uunet!lll-winken!ames!ncar!tank!uwvax!astroatc!nicmad!madnix!aaron
From: aaron@madnix.UUCP (Aaron Avery)
Newsgroups: comp.sys.amiga
Subject: Re: Multiple Serial Ports (Re: vt100 v2.9)
Message-ID: <393@madnix.UUCP>
Date: 15 Jan 89 09:05:19 GMT
References: <8812150227.AA09671@postgres.Berkeley.EDU> <14049@oberon.USC.EDU> <554@sunkisd.CS.Concordia.CA> <3241@sugar.uu.net> <147@ziggy.UUCP> <373@madnix.UUCP> <150@ziggy.UUCP> <385@madnix.UUCP> <154@ziggy.UUCP>
Reply-To: aaron@madnix.UUCP (Aaron Avery)
Organization: ASDG Incorporated
Lines: 21

In article <154@ziggy.UUCP> scotty@ziggy.UUCP (Scott Drysdale) writes:
>controller stop waiting for bytes from the UART and inform the host that
>the transfer is complete without periodically polling the DMA to see if
>anything came in, or adding timers on the serial board to generate interrupts
>if no bytes have arrived after a certain (programmable) delay?  applications

The Z8530 has DMA block transfer support built in. For single byte reads
(perhaps the norm), you set the block length to 1, and the byte will be
stuffed into main memory and you will get an interrupt from the SCC. When
you set the block size to something greater than 1, you don't get an interrupt
until the block transfer is completed. Why would you want to have the serial
board ever generate interrupts if no bytes have arrived (except TBE)? You
handle timeouts on the Amiga, as usual.

Aaron

-- 
Aaron Avery, ASDG Inc.         "A mime is a terrible thing to waste."
                                                             -- Robin Williams
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