Groups > comp.sys.apple2.programmer > #1478

Re: Method to address both Legend and Saturn RAM cards

From	"Anton Treuenfels" <teamtempest@yahoo.com>
Newsgroups	comp.sys.apple2.programmer
References	<dog_cow-1421349003@macgui.com>
Subject	Re: Method to address both Legend and Saturn RAM cards
Date	2015-01-15 22:21 -0600
Message-ID	<crCdnUWW-uNNDCXJnZ2dnUU7-dednZ2d@earthlink.com> (permalink)

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"D Finnigan" <dog_cow@macgui.com> wrote in message 
news:dog_cow-1421349003@macgui.com...

> BANKBASE EQU $C084 ; BASE ADDRESS FOR BANK SELECT ADDR
> RAMTYPE EQU $06 ; TYPE OF RAM CARD INSTALLED
> *
> *
> * SELECT A 16K RAM BANK. DESIRED BANK NUMBER
> * SHOULD BE PASSED IN THE A-REG.
> *
> BANKSEL
> LDA RAMTYPE ; WHAT TYPE OF RAM CARD?
> BEQ :LEGEND ; 0 = LEGEND, 1 = SATURN
> TAX
> STA BANKBASE,X ; SELECT BANK
> RTS
> :LEGEND LDX #0
> STA BANKBASE,X ; SELECT BANK
> RTS

I don't know squat about either card, but:

- if the bank number is passed in the A-register, doesn't the instruction

LDA RAMTYPE

wipe it out first thing?

- if the value of the X-register is zero, there is no practical difference 
between

STA BANKBASE,X

and

STA BANKBASE

unless there's some weird hardware quirk that "notices" the address mode and 
does something special about it.

- so how about this:

BANKSEL
  LDX RAMTYPE
  BEQ LEGEND
  TAX
LEGEND
  STA BANKBASE,X
  RTS

- Anton Treuenfels

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Thread

Method to address both Legend and Saturn RAM cards D Finnigan <dog_cow@macgui.com> - 2015-01-15 19:09 +0000
  Re: Method to address both Legend and Saturn RAM cards "Anton Treuenfels" <teamtempest@yahoo.com> - 2015-01-15 22:21 -0600
    Re: Method to address both Legend and Saturn RAM cards gids.rs@sasktel.net - 2015-01-16 09:41 -0800
      Re: Method to address both Legend and Saturn RAM cards D Finnigan <dog_cow@macgui.com> - 2015-01-16 19:08 +0000
      Re: Method to address both Legend and Saturn RAM cards qkumba <peter.ferrie@gmail.com> - 2015-01-17 21:32 -0800
        Re: Method to address both Legend and Saturn RAM cards gids.rs@sasktel.net - 2015-01-17 22:33 -0800
          Re: Method to address both Legend and Saturn RAM cards gids.rs@sasktel.net - 2015-01-17 22:54 -0800
            Re: Method to address both Legend and Saturn RAM cards Leandro Polimeno <leandro.polimeno@gmail.com> - 2015-02-10 04:53 -0800
              Re: Method to address both Legend and Saturn RAM cards gids.rs@sasktel.net - 2015-02-10 21:19 -0800
                Re: Method to address both Legend and Saturn RAM cards Leandro Polimeno <leandro.polimeno@gmail.com> - 2015-02-11 05:22 -0800
          Re: Method to address both Legend and Saturn RAM cards D Finnigan <dog_cow@macgui.com> - 2015-01-18 10:09 +0000
            Re: Method to address both Legend and Saturn RAM cards "Anton Treuenfels" <teamtempest@yahoo.com> - 2015-01-19 08:33 -0600
              Re: Method to address both Legend and Saturn RAM cards D Finnigan <dog_cow@macgui.com> - 2015-01-19 18:29 +0000
              Re: Method to address both Legend and Saturn RAM cards qkumba <peter.ferrie@gmail.com> - 2015-01-20 09:33 -0800
                Re: Method to address both Legend and Saturn RAM cards "Anton Treuenfels" <teamtempest@yahoo.com> - 2015-01-20 17:06 -0600

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