Re: A86: check keyboard


[Prev][Next][Index][Thread]

Re: A86: check keyboard




You're right routines that reside on page 0 could have been
accessed with a 'jp' instead of a call. I just didn't have the
time to weed through them all, there were more important things
I needed to get done on the 86.  

Later,
Pat

------------------
Original text

From: "Dux Gregis" <assets@eden.rutgers.edu>, on 12/1/98 10:38 PM:

that still doesn't explain why you need call / ret.  especially for calls
like _ldhlind, which doesn't need to swap pages.
>
>if port 5 is $0d, then the address is from page d.  the page switcher
>takes things like this on page 0:
> call $28cb ;it's $28cb in rom 1.2
> .dw $7236 ;address to call
> .db $01 ;page to call
>it saves the current page, reads the address and page from the return
>address provided by THAT call (which is destroyed on the stack) and, when
>the call returns, it restores the current page and returns to whatever
>called the page 0 call.  i hope no one tries to understand that...
>
>-josh
>
>On Tue, 1 Dec 1998 15:56:43 EST ComAsYuAre@aol.com writes:
>>
>>In a message dated 12/1/98 15:49:17 Eastern Standard Time,
>>pmilheron@ti.com
>>writes:
>>
>>> If they were not calls then no bank info is pushed
>>>  onto the stack, and when the routine called exectutes a
>>>  return, page 0Dh would not be paged in when control returns
>>>  to the ASM program.
>>>
>>>  Later,
>>>  Pat
>>>
>>
>>
>>how does the z80 know that an address is from page d?  is that info
>>somehow
>>pushed onto the stack as well as the address?
>>
>
>___________________________________________________________________
>You don't need to buy Internet access to use free Internet e-mail.
>Get completely free e-mail from Juno at http://www.juno.com/getjuno.html
>or call Juno at (800) 654-JUNO [654-5866]



References: