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From: bryce@COGSCI.BERKELEY.EDU.UUCP
Newsgroups: comp.sys.amiga
Subject: Pulling hardware address (eg. $BFF001) from thin bits.
Message-ID: <8705282335.AA06415@cogsci.berkeley.edu>
Date: Thu, 28-May-87 19:35:12 EDT
Article-I.D.: cogsci.8705282335.AA06415
Posted: Thu May 28 19:35:12 1987
Date-Received: Sat, 30-May-87 04:59:39 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 75


Recently there was a discussion about absolute hardware address.  The
conclusion was -> don't pollute the Amiga software base with them <-.
If you need to use a hardware address think about why.	Now think again.
And when your are done with that try to get your job done another way.
If you still need to use the hardware take a look at using the resources.
Now think again.  Still need to use the hardware?  Well don't count on
it being at the same address.

-> In all your Amiga programming you should be using ONE absolute address,
-> location 4, _AbsExecBase, the pointer to the exec.library.

To derive the location of CIAA or CIAB ($BFF001, BFD000 on an Amiga 1000)
use this code:

------- 68000 ---------
		move.l	4,a6		;exec library
		lea.l	CIAAName(pc),a1
		jsr	_LVOOpenResource(a6)
		tst.l	d0		;grrr... bah, humbug gritch gripe.
		beq.s	e_nociaa
		move.l	d0,a1
		move.l	CR_HWADDR(a1),CIAABASE	;This is it!
		jsr	_LVOCloseLibrary(a6)
		tst.l	CIAABASE
		beq.s	e_nociaa	;no cia? incompatible machine...
		...

CIAAName	dc.b	'ciaa.resource',0
-------- C -----------
struct Library *MyCIAbase

MyCIAbase=(struct Library*)OpenResouce("ciaa.resource");
 if(MyCIAbase==NULL) goto diehorribly;
ciaaaddr=MyCIAbase->CR_HWADDR;
CloseLibrary(myCIAbase);
 if(ciaaaddr==NULL) goto croak;
----------------------

This only has to be done once. (unless someone removes/adds a CIA while
 the machine in running :-) :-) :-) :-)
Now if you tried to assemble/compile this you would get a undefined symbol
on CR_HWADDR.  You need a structure, (68000 flavor only):

	   STRUCTURE	CIAR,LIB_SIZE
		APTR	CR_HWADDR	;Hardware address
		UWORD	CR_IntMask
		UBYTE	CR_IEnable
		UBYTE	CR_IActive
		STRUCT	CR_INTNODE,IS_SIZE
		STRUCT	CR_ITVA,IS_SIZE
		STRUCT	CR_ITVB,IS_SIZE
		STRUCT	CR_IVALRM,IS_SIZE
		STRUCT	CR_IVFLAG,IS_SIZE
		LABEL	CR_SIZE

(Or just replace CR_HWADDR in the examples with LIB_SIZE, they are the same)

--- Documentation bug #1 ---
This structure IS NOT on any of the Gamma 1 include files disks.  It was
probably an accident that it was printed out on page E-72 of the RKM.
--- Documentation bug #2 ---
The autodocs for the OpenResource function direct ones attention to the
CloseResource function.  'Taint so, there is no such beast.
--- Documentation bug #3 ---
How to derive the base address of CIAA, CIAB and CUSTOM is NOT documented
ANYWHERE.					 ^^^^^^
--- Documentation bug #4 ---
Include file exec/memory.i.  "APTR MC_SIZE" should read "LABEL MC_SIZE".
-------------
         Ack!  (NAK,EOT,SOH)
 |\ /|  .
 {o O} .  bryce@cogsci.berkeley.EDU -or- ucbvax!cogsci!bryce
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