Re: Apple II plus memory map needed + other help :)

[CUTjblakeney@sympatico.ca (Jeff Blakeney)]

On Sun, 24 Feb 2002 13:29:30 -0000, "andy welburn"
<warlords@ntlworld.com> wrote:

>first post here.. so don't flame me, i have lookedm but i can't understand
>the memory maps and other information that i am finding..
>
>I have an apple 2 plus sitting here that i am trying to bring back to life,
>the power supply is good, that i do know, the cpu is running ok (no resets)
>but no video output..
>
>I fix video arcade pcb's all the time, and have a Fluke 9100 digital test
>system, and a 6502 pod.. i could do preliminary tests to work out whats
>wrong, if only i had a reliable memory map..
>
>for example, Missile Command (6502 based) is like this:
>
>0000-3FFF = ram
>5000-7FFF = Program ROM
>
>i'm only really interested in ram/rom locations as i can run tests on those,
>i don't need to know input ports or other stuff..
>
>The only other thing i need to know is if there's any banked memory or rom
>or something, need to know if and where the switches are..

Well, the responses so far have given you a basic map but here is a
little more detailed one:

     E000-FFFF ROM
     D000-DFFF Language card
     C800-CFFF RAM that can also be shared by cards in slots
     C100-C7FF Each page of 256 bytes is mapped to slots 1 to 7
     C000-C0FF Soft switches
     6000-BFFF Free RAM
     4000-5FFF Hi-Res page 2
     2000-3FFF Hi-Res page 1
     0C00-1FFF Free RAM
     0800-0BFF Text page 2
     0400-07FF Text page 1
     0300-03FF Vectors (lower section is actually free RAM)
     0200-02FF Input Buffer
     0100-01FF Stack
     0000-00FF Zero page

Also note that the language card and ROM areas are bank switchable.
You can select either ROM or RAM in the area of E000-FFFF and if you
select RAM you have the option of write protecting it or not.

You may have noticed that the D000-FFFF area is only 12 KB and the
language cards that were used in slot 0 of the II and II+ (and built
into the IIe and later) is 16 KB so there is an extra 4 KB that you
can access.  This is done by selecting bank 1 or bank 2 of 4 KB in the
D000-DFFF area.

The soft switches associated with the selections are:

     C088 or C08C selects RAM in E000-FFFF
                  selects bank 1 in D000-DFFF
                  write protects RAM
                  needs to be toggled once to activate

     C08B or C08F selects RAM in E000-FFFF
                  selects bank 1 in D000-DFFF
                  write enables RAM
                  needs to be toggled twice to activate

     C08A or C08E selects ROM in D000-FFFF
                  write protects RAM
                  needs to be toggled once to activate
                  (note: writes to D000-FFFF do nothing,
                   reads from D000-FFFF will return what is in ROM)

     C089 or C08D selects ROM in D000-FFFF
                  write enables RAM
                  needs to be toggled twice to activate
                  (note: writes to D000-FFFF will change RAM,
                   reads from D000-FFFF will return what is in ROM)


     C080 or C084 selects RAM in E000-FFFF
                  selects bank 2 in D000-DFFF
                  write protects RAM
                  needs to be toggled once to activate

     C083 or C087 selects RAM in E000-FFFF
                  selects bank 2 in D000-DFFF
                  write enables RAM
                  needs to be toggled twice to activate

     C082 or C086 selects ROM in D000-FFFF
                  write protects RAM
                  needs to be toggled once to activate
                  (note: writes to D000-FFFF do nothing,
                   reads from D000-FFFF will return what is in ROM)

     C081 or C085 selects ROM in D000-FFFF
                  write enables RAM
                  needs to be toggled twice to activate
                  (note: writes to D000-FFFF will change RAM,
                   reads from D000-FFFF will return what is in ROM)

I'm not an expert on this and I'm using information from the book
"Inside the Apple IIgs" so there may be some inaccurate information.
I'm sure that there are others here who can point out any problems and
give you more information if you need it.

--
 Jeff Blakeney - Dean of the Apple II Unversity on A2Central.com
               - CUT the obvious from my address to e-mail me