Re: A86: Re: LCD stuff
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Re: A86: Re: LCD stuff
here's how the rom does the checksum. unfortunately there's no page d
equivalent.
calling $4101 will do this checksum before turning off the calc. in
fact, ti calls this _setChecksum
0dfb 3e42 ld a,#42
0dfd d306 out (#06),a
0dff dde5 push ix
0e01 dd210080 ld ix,#8000
0e05 01ff3f ld bc,#3fff
0e08 210800 ld hl,#0008
0e0b 54 ld d,h
0e0c dd5e00 ld e,(ix+#00)
0e0f dd23 inc ix
0e11 19 add hl,de
0e12 0b dec bc
0e13 79 ld a,c
0e14 b0 or b
0e15 20f5 jr nz,#0e0c
0e17 5a ld e,d
0e18 eb ex de,hl
0e19 ed52 sbc hl,de
0e1b dde1 pop ix
0e1d c9 ret
-josh
On Fri, 19 Nov 1999 18:35:58 -0800 (PST) Matt C <snoborder420@yahoo.com>
writes:
>
>are you going to release the code for the new version
>of ZAC?
>this little tip would be great to use in onther
>programs or a shell
>
>--- Clem <darkclem@wanadoo.fr> wrote:
>>
>> > As near as I can tell, if the cpu hits $0000, the
>> calc's going to be reset.
>> > Somehow, when the lithium battery is in there,
>> that doesn't happen. But
>> > why?
>>
>> I know !!! :) I use a trick in the (upcoming) ZAC
>> memory recovery system...
>> When the cpu hits $0000, the TI-OS will test a
>> checksum to determine
>> whether the calc has been turned off correctly, or
>> crashed...
>> This checksum is located at _onCheckSum, and it's
>> the 16 bit sum of the
>> whole ram page 2... if you set this checksum
>> correctly and your program
>> crashes, when you remove one battery, put it back in
>> and turn the calc on,
>> it should work as if it was turned off correctly ;-)
>>
>> ---
>> Clem Vasseur <darkclem@wanadoo.fr>
>> Icarus Productions <http://icarus.ticalc.org>
>>
>>
>>
>>
>
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