Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!apple!dlyons
From: dlyons@Apple.COM (David A. Lyons)
Newsgroups: comp.sys.apple2
Subject: Re: Playing (rough) with CDA's
Message-ID: <42601@apple.Apple.COM>
Date: 3 Jul 90 08:34:20 GMT
References: <1990Jul2.062757.2290@rbdc>
Distribution: usa
Organization: Apple Computer Inc, Cupertino, CA
Lines: 31

In article <1990Jul2.062757.2290@rbdc> barry@rbdc.UUCP (Barry Newberry) writes:
>As far as I can tell, you can install CDA's (Toolbox #$0F05), but
>you can't remove them (nicely).

This is mostly correct.  You *can* remove them, with RemoveNDA and RemoveCDA,
added for System Software 5.0.  The thing is you have to know the right
Handle to pass to those calls, and the system provides no way to get the
handles.  The only reliable way is to remove only DAs that your program
installed itself & recorded the handles somewhere (say, in the MessageCenter).

> [...] where can I find the [guaranteed] counter for the number of CDA's ?

There's no guaranteed way.

>I am heavily into Assembly; I've written a SCC 8530 interrupt
>handler using the SCC(chan)REG and SCC(chan)DATA softswitches to do
>everything. (It works, but I have no way of knowing if I've taken all
>of the proper steps for the Init.) All I need is the Technical Info.

I don't know if it will answer all your questions, but check out GS
Technical Note #18 by Jim Luther ("Do-It-Yourself SCC Access").  The
revision I have here (at home) is March 90.  Not sure if it was revised
in May, but it is being revised for July.
-- 
David A. Lyons, Apple Computer, Inc.      |   DAL Systems
Apple II Developer Technical Support      |   P.O. Box 875
America Online: Dave Lyons                |   Cupertino, CA 95015-0875
GEnie: D.LYONS2 or DAVE.LYONS         CompuServe: 72177,3233
Internet/BITNET:  dlyons@apple.com    UUCP:  ...!ames!apple!dlyons
   
My opinions are my own, not Apple's.