Re: Sv: Sv: A83: Re: Re:

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Re: Sv: Sv: A83: Re: Re:


Well, so was I. Just because I write a mail it doesn't mean that I'm flaming
someone (although I can understand why you think so... =)).

Linus

On 17-Sep-98, Joe Wingbermuehle wrote:

>I think he was just trying to expand on his, and everyone elses',
>understanding of the ret instruction.  His version would obviously take more
>clocks, more bytes (and destroy hl), but it does explain what is happening.

> ex (sp),hl
> inc sp
> inc sp
> jp (hl)

>All possible!

>Joe Wingbermuehle
>http://www.usmo.com/~joewing/

>-----Original Message-----
>From: Linus Akesson <lairfight@softhome.net>
>To: Thomas Turn Jensen <assembly-83@lists.ticalc.org>
>Date: Wednesday, September 16, 1998 3:07 PM
>Subject: Re: Sv: Sv: A83: Re: Re:


>>
>>Yes, it looks like assembler. But as you said yourself, some of the
>>instructions are not possible on the z80. The code fragment is meant to
>>explain/emulate a ret, which is exactly what it does.
>>Why ret would trash hl? Well, it doesn't! But in your version of The Ret
>>Emulator hl is in fact trashed. Thus, the code doesn't emulate a ret and
>thus
>>my message.
>>
>>Linus
>>
>>On 16-Sep-98, Thomas Turn Jensen wrote:
>>
>>>Honestly I don't see what you mean. First, it sure looked like assembler
>to
>>>me, 2nd why would ret trash hl (and what has that got to do with it?)
>>
>>>(sorry if I've gotten all this wrong... :-)
>>
>>>-----Oprindelig meddelelse-----
>>>Fra: Linus Akesson <lairfight@softhome.net>
>>>Til: Thomas Turn Jensen <assembly-83@lists.ticalc.org>
>>>Dato: 15. september 1998 20:59
>>>Emne: Re: Sv: A83: Re: Re:
>>
>>
>>>>
>>>>Oh please... That was pseudo code describing the ret instruction. Your
>code
>>>>might compile better, but ret doesn't trash hl, does it?
>>>>
>>>>Linus
>>>>
>>>>On 15-Sep-98, Thomas Turn Jensen wrote:
>>>>
>>>>>Not that it's very important but couldn't you just have this instead of
>>ret:
>>>>
>>>>>lh hl,(sp)      ; not possible :(
>>>>>dec sp
>>>>>dec sp
>>>>>ld pc,hl        ; not possible
>>>>
>>>>>Anyways, loading pc isn't possible according to the Tasm80.tab so this
>is
>>>>>quite meaningles.
>>>>
>>>>
>>>>>***
>>>>>Thomas Turn Jensen
>>>>>Icq uin => 8128636
>>>>>IRC, Undernet => Mukke
>>>>>***
>>>>>Får computeren dig til at sukke?
>>>>>Så kald da blot på Mukke
>>>>>***
>>>>
>>>>
>>>>>-----Oprindelig meddelelse-----
>>>>>Fra: Alan C Johnson <benjamin99@juno.com>
>>>>>Til: assembly-83@lists.ticalc.org <assembly-83@lists.ticalc.org>
>>>>>Dato: 13. september 1998 22:22
>>>>>Emne: Re: A83: Re: Re:
>>>>
>>>>
>>>>>>
>>>>>>The stack pointer points to the memory location in the RAM that is used
>>>>>>for the stack.  Now here's a little bit of useless info.  By the way,
>>>>>>does anyone know where thestack memory starts and ends
>>>>>>
>>>>>>Basically, if there was no push command, you would have to do this:
>>>>>>
>>>>>> inc sp ; 2 because the stack locations are 16-bits
>>>>>> inc sp
>>>>>> ld (sp),rr
>>>>>>
>>>>>>Pop would be:
>>>>>> ld rr,(sp)
>>>>>> dec sp
>>>>>> dec sp
>>>>>>
>>>>>>Call would be:
>>>>>> inc sp
>>>>>> inc sp
>>>>>> ld (sp),pc
>>>>>> jp xxxx ; jp actually being ld pc,xxxx
>>>>>>
>>>>>>Ret would basically be:
>>>>>> ld pc,(sp) ; which would actually be impossible, because it would jump
>>>>>>as soon as you
>>>>>> dec sp ; loaded the pc register, so it wouldn't post-decrement the
>>>>>>stack pointer
>>>>>> dec sp
>>>>>>
>>>>>>
>>>>>>>
>>>>>>>Would someone like to explain the stack pointer in more detail?  I
>>>>>>>know
>>>>>>>*roughly* what it does...no, actually I don't :)...
>>>>>>>
>>>>>>>Later,
>>>>>>>
>>>>>>>James Matthews (matthews@tkb.att.ne.jp)
>>>>>>>
>>>>>>>ICQ: 7413754
>>>>>>>http://home.att.ne.jp/gold/tomcat21/index.html
>>>>>>>http://library.advanced.org/18242/
>>>>>>>
>>>>>>>----------
>>>>>>>> From: Scott Dial (Revenant) <homosapian@geocities.com>
>>>>>>>> To: assembly-83@lists.ticalc.org
>>>>>>>> Subject: A83: Re:
>>>>>>>> Date: Sunday, September 13, 1998 9:28 AM
>>>>>>>>
>>>>>>>>
>>>>>>>> Exactly that...
>>>>>>>>
>>>>>>>> sp is a z80 register for the position of stack pointer... so that he
>>>>>>>can
>>>>>>>> return to that exact point later. spbak is defined at the bottom:
>>>>>>>spbak
>>>>>>>> .dw $0000
>>>>>>>>
>>>>>>>> Patrick W Bambrough wrote:
>>>>>>>> >
>>>>>>>> > hey can anyone tell me what this means and if there is an 83
>>>>>>>equivelant??
>>>>>>>> > ld (spbak),sp
>>>>>>>>
>>>>>>>> --
>>>>>>>> Scott Dial
>>>>>>>> revenant_1@hotmail.com
>>>>>>>> ICQ#3608935
>>>>>>>
>>>>>>
>>>>>>_____________________________________________________________________
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>>>>>>
>>>>
>>>>
>>>>
>>>>
>>
>>
>>
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