Re: A86: Re: Re: new emulator

To: assembly-86@lists.ticalc.org
Subject: Re: A86: Re: Re: new emulator
From: rabidcow@juno.com
Date: Sat, 16 Oct 1999 02:30:53 -0700
Reply-To: assembly-86@lists.ticalc.org

that may be, but that's not what they're doing here. (why would they do
that???  don't they have enough memory??  why don't they just setup a
stack frame and use ix like other places??)

the value saved on the stack is put back without ever reading the $80
back in:
  ld      d,a
  in      a,(#06)
  push    af
  ld      a,#80
  out     (#06),a
  ld      a,d
  ld      (#8000),a
  pop     af
  out     (#06),a
  ld      a,d
  ret

i can't really explain this behavior, myself.
i say load $00 to port 5, $80 to port 6 and comparing the two pages.

where's pat when you need him? :)

-josh

On Thu, 23 Dec 1999 18:43:18 -0700 "Kirk Meyer" <kirkmeyer@bigfoot.com>
writes:
>
>Many times, TI uses port 6 as a temporary storage place.
>
>----- Original Message -----
>From: Liyang Hu <liyang@liyang.freeserve.co.uk>
>To: TI-Emu ML <ti-emulator@lists.ticalc.org>; TI-86 Asm ML
><assembly-86@lists.ticalc.org>
>Sent: Thursday, December 23, 1999 2:26 PM
>Subject: A86: Re: new emulator
>
>
>>
>> hmm... thanks for prompting me to look at my code again - after 
>messing
>with
>> TI86Emu for a while, I managed to find the bit of code that's 
>messing my
>> emulator up. It gets here straight after a keypress...
>> Around 0x6960, ROM page 0x0a, we see this chunk of code:
>>
>> 6957  IN A,($06)
>> 6959  PUSH AF
>> 695A  LD A,$80
>> 695C  OUT ($06),A
>> 695E  LD A,D
>> 695F  LD ($8000),A
>> 6952  POP AF
>>
>> that's definitely writing to the ROM... (unless bit 7 of port 6 
>actually
>> does something... I was under the impression that this bit was 
>ignored,
>ne?)
>> My emu crashes at 6960, just as it attempts the write.
>> I can see TI86Emu going through this bit of code as well, but it 
>ignores
>the
>> write, as far as I can tell. Now, my question is: WTF is it doing 
>writing
>to
>> the ROM ?!?!?!? That's just going to make my code a lot more
>complicated...
>> (I'm not checking whether the mem is writable or not, for speed 
>reasons. I
>> suppose I could always patch the ROM? What do you guys think?)
>>
>> > At what address in the ROM does it do this?  Some devices will
>> > use writes to
>> > ROM as hardware control registers, but the calc doesn't do this.
>> >
>> > > Should the ROM (program) be trying to write to the ROM (memory)
>> > during its
>> > > execution?
>>
>> sayoonara!
>> --
>>  /*\-------------------------.   .----------------------------.
>> |    Liyang Hu aka DenseBoy   \ /   __pikachu ICQ # 39391385   \
>> |     http://www.nerv.cx/      |    <denseboy@41t4v¡5t4.n3t>    |
>> +------------------------------+--------------------------------+
>> |  When you say "I wrote a program that crashed Windows",       |
>> |    people just stare at you blankly and say:                  |
>> |      "Hey, I got those with the system, *for free*".          |
>> |   -----------------------------------------------------------/
>>  \*/ /*  get my public key at http://www.nerv.cx/liyang.asc  */
>>     /*   decode the l33t-speak in my address to email me!   */
>>
>>
>
>

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Follow-Ups:
Re: A86: Re: Re: new emulator
From: "Kirk Meyer" <kirkmeyer@bigfoot.com>