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From: sec1918@uxf.cso.uiuc.edu
Newsgroups: comp.sys.apple
Subject: Re: IIgs Software Reboot
Message-ID: <48000012@uxf.cso.uiuc.edu>
Date: 14 Dec 89 10:38:42 GMT
References: <1949868@mtsg.ubc.ca>
Lines: 76
Nf-ID: #R:mtsg.ubc.ca:1949868:uxf.cso.uiuc.edu:48000012:000:2717
Nf-From: uxf.cso.uiuc.edu!sec1918    Dec 13 15:28:00 1989


Referring to Apple IIgs tech note #49 "Rebooting (Really)"...

The Easy Way
GS/OS provides a mechanism for rebooting with the OSShutdown call.  This call,
documented in volume 1 of the GS/OS reference, will either reboot the system
(after first shutting down all loaded and generated drivers and closing all 
open sessions) or will shut down everything and present a dialog box which 
states, "You may now power down your Apple IIgs safely"...

  ok this is like choosing shut down from the finder...

also it mentions that OSShutdown can resize the ramdisk if it wants.  
"You should always use OSShutdown when using GS/OS"...

ok but GS/OS sucks huge, so they also provide

The Hard Way

Programs not using GS/OS have a little more work to do.  The supported 
non-GS/OS method of rebooting is similar to the method used on 8-bit machines: 
change the value of POWERUP ($00/03F4) and do a long jump to RESET ($FA62).  
However, there are a few catches:

1. the jump must be made in emulation mode.
2. Interrupts must be disabled.
3. The data bank register must be set to zero.
4. The direct page must be zero.
5. ROM firmware must be visible in the memory map.
6. Internal interrupt sources (such as the ones for AppleTalk) must be shut down

Simply disabling interrupts without shutting down AppleTalk intterupt sources 
inside the system will cause the system to hang when the jump to RESET is made.

Turning off these internal interrupt sources is accomplished by changing
softswitch values at $C039 (SCCAREG), $C041 (INTEN), and $C047 (CLRVBLINT).

The following code example demonstrates the correct method:

POWRUP	equ	$0003F4		;power up byte in bank zero
STATEREG equ	$C068		;ROM/RAM state register
CLRVBLINT equ 	$C047		;clear VBL intterupt flags register
INTEN	equ	$C041		;interrupt enable register
SCCAREG equ	$C039		;SCC register
RESET	equ	$00FA62		;ROM reset entry point

FROMNATV anop			;must be in native mode here
	sei
	pei	0
	pei	0		;push four zero bytes
	plb
	plb			;pull data bank register (must do twice)
	pld			;pull 16-bit data bank register
	sec
	xce			;emulation mode
	longa off
	longi off
FROMEMUL anop
	sei
	dec	POWRUP		;invalidate power up byte
	lda	#$0C		;rom parameters
	sta	STATEREG	;swap in the ROM and everything else out
	stz 	CLRVBLINT	;clear VBL interrupts
	stz	INTEN		;turn off internal interrupt sources
	lda	#$C0
	sta	SCCAREG
	jml	RESET		;kablamm

I must state that this was copied almost exactly from the tech note but hasn't
been tried so there may be some bugs... I dunno it looks good to me.

"All opinions above are those of Apple Computer, Inc., not me."

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