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From: bson@rice-chex.ai.mit.edu (Jan Brittenson)
Newsgroups: comp.sys.handhelds
Subject: Re: Chip question
Message-ID: <12400@life.ai.mit.edu>
Date: 13 Dec 90 12:03:22 GMT
References: <F002EC16567F006FAC@ISUVAX.BITNET>
Sender: news@ai.mit.edu
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In article <F002EC16567F006FAC@ISUVAX.BITNET> TNAN0@CCVAX.IASTATE.EDU writes:

 > I've been trying to write some stand alone (non-RPL-stack dependent)
 > programs...  What's the best way to locate and access relative memory
 > addresses?  For example, if I have a data area at the beginning of my
 > code, it seems to me the best way to access it would be to use a
 > thisone move.a pc,a" followed by a "move.p5 thisone-dataarea,c"
 > sub.a c,a" thus leaving the address

   STAR 1.02.3 and later comes with a macro ADDR in hp48.star. The
macro is used as follows:


	ADDR	location, dest


Where `location' is any expression and `dest' is either C, A, D0, or D1.
An example:

	; ...

	addr	foo, c

	; ...

foo:	ascii	`Hello world!'


   The code generated is much what you describe, although ADD is used
instead of SUB. A.a is used for temporary storage, unless the
destination is A, in which case C.a is used as a temporary register.
The macro can easily be modified to take an optional third argument to
specify which register to use for temporary storage.

For the insanely curious, I'll include the macro definition.

						-- Jan Brittenson
						   bson@ai.mit.edu

	macro	addr  operand, dest

	save	sym
	sym  = gensym

	save	tmp
	save	ntmp

	dest = uc^`$dest'

	if `$dest' == `A'
	  tmp = `C'
	  ntmp= `A'
	else
	  tmp = `A'
	  ntmp= `C'
	endif

	move    pc, $tmp
	$sym = .

	if (`$dest' == `D0') || (`$dest' == `D1')
	  move.5 ($operand)-$sym, $dest
	  swap    $ntmp, $dest
	  add.a   $tmp, $ntmp
	  swap    $ntmp, $dest
	else
	  move.p5 ($operand)-$sym, $dest
	  add.a   $tmp, $dest
	endif
	
	restore	tmp
	restore	ntmp
	restore sym

	endmacro