Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!snorkelwacker.mit.edu!ai-lab!rice-chex!bson
From: bson@rice-chex.ai.mit.edu (Jan Brittenson)
Newsgroups: comp.sys.handhelds
Subject: Re: HP48: mcode question
Message-ID: <12289@life.ai.mit.edu>
Date: 8 Dec 90 00:29:08 GMT
References: <kskalb.660423859@faui1f>
Sender: news@ai.mit.edu
Organization: nil
Lines: 58

In article <kskalb.660423859@faui1f> 
   kskalb@faui1f.informatik.uni-erlangen.de (Klaus Kalb) writes:

 > I need a way to push CPU-regs to the RPL-stack during mcode-execution
 > and have my mcode continuing.

   The SPRITE routine I posted a couple of weeks ago does this with a
`swap_regs' routine. Instead of saving or restoring the RPL context,
it swaps it with your registers. Use it to temporarily switch to an
RPL context by swapping, manipulating the stack, and swapping again
when done. If you want to push a number as a short (system binary),
for instance, you can stick the value in R0, swap context, call the
routine to push R0 as a short on the stack, and swap back.

I've cut it out for you here - others may find it useful as well.


O  /
 \/
 /\ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
O  \


; Switch in/out of RPL context. Wrecks C.a.

TOH=#705b0
TOS=#70579
FP=#70574
Free_size=#7066e

swap_regs:
	move.a	a,c
	push.a	c

	swap.a	c,d0
	move.5	TOH,d0
	move.a	@d0,a
	move.a	c,@d0

	move.5	TOS,d0
	move.a	@d0,c
	swap.a	c,d1
	move.a	c,@d0

	move.5	FP,d0
	move.a	@d0,c
	swap.a	c,b
	move.a	c,@d0

	move.5	Free_size,d0
	move.a	@d0,c
	swap.a	d,c
	move.a	c,@d0

	move.a	a,d0
	pop.a	c
	move.a	c,a
	ret