[A83] Re: Explaining the stack for registers

To: <assembly-83@lists.ticalc.org>
Subject: [A83] Re: Explaining the stack for registers
From: "Ronald Teune" <rtwolf@gmx.net>
Date: Tue, 21 Aug 2001 18:43:12 +0200
Reply-To: assembly-83@lists.ticalc.org

>Sure...
>
>  push  hl
>  call  routine
>  ...           ; don't pop
>
>routine:
>  pop   hl      ; return address in HL
>  ex    (sp),hl ; return address on stack, pushed HL back in HL

Ah. Ofcourse. ex strikes again...

>  ...
>  ret           ; safe to return



push hl
>  call Routine
>
>Routine:
> pop de      ; remove return address

Yeah, but this destroys de

  pop hl      ; get HL, why do you want to this ?????

Just wondering... :-)

  push de     ; ret address back to stack
>  ret


Thanks to you two.
    --Ronald

>>From: "Ronald Teune" <rtwolf@gmx.net>
>>Reply-To: assembly-83@lists.ticalc.org
>>To: <assembly-83@lists.ticalc.org>
>>Subject: [A83] Re: Explaining the stack for registers
>>Date: Fri, 17 Aug 2001 21:45:31 +0200
>>
>>
>> >Also note that CALL and RET also use the same stack...
>> >
>> >You can't:
>> >
>> >  push hl
>> >  call Routine
>> >
>> >Routine:
>> >  pop hl
>> >  ret
>>
>>But is there ANY way to push/pop through calls?
>>
>> >If you did that, HL would contain the address of the code after the
call,
>> >and the RET would jump to the value of the pushed HL.  In other words,
>> >CRASH.
>> >
>> >(Unless of course HL contained a valid executable address...)
>> >
>> >>From: "TypeR unknown" <typerfuture@hotmail.com>
>> >>Reply-To: assembly-83@lists.ticalc.org
>> >>To: assembly-83@lists.ticalc.org
>> >>Subject: [A83] Re: Explaining the stack for registers
>> >>Date: Thu, 16 Aug 2001 19:51:46 +0200
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>> >>
>> >>
>> >>Ahh I understand much better now!!!
>> >>I thought that every register that can be pushed had it's own stack, so
>>I
>> >>was a bit confused when it appeared that the content of one register
>>could
>> >>somehow be loaded in another register, but I understand very well now,
>> >>thank
>> >>you very much for your explanation!
>> >>
>> >>
>> >> >From: "Michael Vincent" <hookman@worldnet.att.net>
>> >> >Reply-To: assembly-83@lists.ticalc.org
>> >> >To: <assembly-83@lists.ticalc.org>
>> >> >Subject: [A83] Re: Explaining the stack for registers
>> >> >Date: Thu, 16 Aug 2001 10:12:18 -0700
>> >> >
>> >> >
>> >> >First, "if you push af and then pop bc" the contents will be in BC,
>>not
>> >>AF.
>> >> >The reason for this is when you push a register, the values in it are
>>put
>> >> >on
>> >> >the stack, not the name. So if you push af then the value of A and
the
>> >> >flags
>> >> >byte are on the stack. You can then pop whatever you want. If you pop
>>bc
>> >> >then the 2 bytes on the stack from the push af will be put in BC. (B

>>will
>> >> >have what was in A, and C will have what was in F).
>> >> >
>> >> >There is no limit to how many times a register can be pushed, except
>>on
>> >>the
>> >> >TI-83 Plus (and I think 83) the stack is only 400 bytes. After that
>>you
>> >> >will
>> >> >corrupt RAM. The TI-OS uses a few bytes, but you have like 100 pushes
>>or
>> >> >more you could do before you overflowed the stack.
>> >> >
>> >> >
>> >> >Michael Vincent
>> >> >Detached Solutions - www.detacheds.com
>> >> >Radical Software - www.radicalsoft.org
>> >> >
>> >> >----- Original Message -----
>> >> >From: "TypeR unknown" <typerfuture@hotmail.com>
>> >> >To: <assembly-83@lists.ticalc.org>
>> >> >Sent: Thursday, August 16, 2001 10:00 AM
>> >> >Subject: [A83] Explaining the stack for registers
>> >> >
>> >> >
>> >> > >
>> >> > > After reading the FAQ in AsmGuru there is a question about the
>>stack
>> >> >with
>> >> > > registers. It says that (if I remember correctly) "if you push af
>>and
>> >> >then
>> >> > > pop bc, the contents of bc will be in af"
>> >> > >
>> >> > > WHY ???
>> >> > >
>> >> > > I see no logic in that, and unfortunatly it isn't explained in
>>AsmGuru
>> >> > > either, so here I am :)
>> >> > >
>> >> > > Also I would like to know how many times a register can be pushed.
>> >> > >
>> >> > >
>> >> > >
>> >> > >
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