XL/XE Diag rom mapping?

XL/XE Diag rom mapping?

Post by Peter Be » Thu, 09 Feb 1995 04:41:30



Another stupid question, can anybody tell me precisely what the effect
on the memory mapping is when you turn on the 'enable diagnostic ROM' bit
on PB7.

I've just discovered (after about 1 1/2 years!) that if you type 'BYE' on
my modified 800 the system crashes :(.  The ROM image looks OK, so I
think the decode logic must be confused.

Pete
--

 
 
 

XL/XE Diag rom mapping?

Post by ben co » Thu, 09 Feb 1995 15:57:21


>Another stupid question, can anybody tell me precisely what the effect
>on the memory mapping is when you turn on the 'enable diagnostic ROM' bit
>on PB7.

>I've just discovered (after about 1 1/2 years!) that if you type 'BYE' on
>my modified 800 the system crashes :(.  The ROM image looks OK, so I
>think the decode logic must be confused.

>Pete
>--  


How is your 800 modified?


 
 
 

XL/XE Diag rom mapping?

Post by PATERSON, DAVID ANDR » Thu, 09 Feb 1995 16:36:00



>Another stupid question, can anybody tell me precisely what the effect
>on the memory mapping is when you turn on the 'enable diagnostic ROM' bit
>on PB7.

>I've just discovered (after about 1 1/2 years!) that if you type 'BYE' on
>my modified 800 the system crashes :(.  The ROM image looks OK, so I
>think the decode logic must be confused.

I think that the self-test runs somewhere in the middle of memory, replacing
RAM.  On an 800, though, it should go to MEMO PAD MODE - remember that?  It's
why I got an Atari in the first place - I discovered the full screen editor and
was hooked.  That, and Protector from Synapse.

Dave

 
 
 

XL/XE Diag rom mapping?

Post by Peter Be » Fri, 10 Feb 1995 19:07:39




> >Another stupid question, can anybody tell me precisely what the effect
> >on the memory mapping is when you turn on the 'enable diagnostic ROM' bit
> >on PB7.

> >I've just discovered (after about 1 1/2 years!) that if you type 'BYE' on
> >my modified 800 the system crashes :(.  The ROM image looks OK, so I
> >think the decode logic must be confused.

> >Pete
> >--  

> How is your 800 modified?

Heavily 8-) -- It's switchable between 800 w/256K Axlon lookalike, 130XE
and 320XE.  I've got both OS ROMS and BASIC in one EEPROM (27C512), and
a big PLD to switch everything around.  Oh, and there is an extra PIA that
gets switched in in place of joysticks 3 and 4 when you turn on the XL/XE
OS.  It still doesn't have a PBI though - maybe I should work on that...

I was just about to start writing it all up for the amusment of the 8bit
community, and discovered this little problem, which I'd like to resolve
before I release the mod docs.  

Pete
--

 
 
 

XL/XE Diag rom mapping?

Post by Peter Be » Fri, 10 Feb 1995 19:10:08





> >Another stupid question, can anybody tell me precisely what the effect
> >on the memory mapping is when you turn on the 'enable diagnostic ROM' bit
> >on PB7.

> >I've just discovered (after about 1 1/2 years!) that if you type 'BYE' on
> >my modified 800 the system crashes :(.  The ROM image looks OK, so I
> >think the decode logic must be confused.

> I think that the self-test runs somewhere in the middle of memory, replacing
> RAM.  On an 800, though, it should go to MEMO PAD MODE - remember that?  It's
> why I got an Atari in the first place - I discovered the full screen editor and
> was hooked.  That, and Protector from Synapse.

Well, it does go to memo pad - when I switch in the 800 ROMs.  I should have
been a bit clearer, the machine has two sets of ROMS in it.  The problem
occurs when the XL/XE ROMS are selected.

Pete
--

 
 
 

XL/XE Diag rom mapping?

Post by Rick_Michael_Cort.. » Fri, 10 Feb 1995 23:40:08


Pete, once again I don't fool around with PBI stuff so most of what I
say is either a guess or from Mapping The Atari. In my other post I said
something to the effect of I didn't know how the remap of PBI ROM works.
If I really had the time, I could disassemble the ROM & find out, but
I have little desire to do something with the buss so... There are plenty
of rumors about people that supported the Atari, like CSS, disassembled
the entire XL OS for building stuff like the Black Box. Atari themselves
never released the source code & everybody who may have a copy of the
OS they produced themselves treats it as a trade secret. That's fair since
they are under no obligation to help somebody compete with them, but it
makes it a little harder to figure out what's going on. I'm not sure exactly
what your modified xl is like, but absolutely one of the first things to go
when people were looking for PIA pins for memory expansion were things
like built in basic & I'd guess ROM diagnostics. The other thing that
went was the ROM diagnostics in the OS in all the modified OS chips out
there. I believe when the ROM diagnostics are active, the OS ROM that has
that piece of code is $4000 area similar to the way ram banks are switched
in & out. How it's called once it gets there, i.e. JSR $4000 or JMP $4000
or JMP $???? I don't know. Ditto for the PBI stuff. The bright side is
Mapping gave the address of the generic parallel device handler vector!
It says to just move the vector into the the regular device handler table
along with the device name. Thats how the 1450 added the V:(oice) handler.
If this is accurate, the address contained in $E48F-$E490 will point some
where in the ROM to the PBI initialization & I/O vector tables just like
the ones at $E400 area do. Are you up for some disassembling?
Rick
 
 
 

XL/XE Diag rom mapping?

Post by Matthias Beli » Sun, 12 Feb 1995 00:28:12



>Well, it does go to memo pad - when I switch in the 800 ROMs.  I should have
>been a bit clearer, the machine has two sets of ROMS in it.  The problem
>occurs when the XL/XE ROMS are selected.

Well, the problem is very easy to solve !
When pin 7 of port B is switched, the part of the ROM from $D000 until $d7ff
(which can't be used normally because of the I/O Adresses )  is mirrored
to   $5000 and there is the self test of the XL-machines.
It's a very simply logic managed by the MMU.
I've had the description of the MMU , but it's not so difficult to find it
out !

Matt

 
 
 

XL/XE Diag rom mapping?

Post by richard.b.de » Sat, 11 Feb 1995 23:04:59



<deletions>

Quote:>like built in basic & I'd guess ROM diagnostics. The other thing that
>went was the ROM diagnostics in the OS in all the modified OS chips out
>there. I believe when the ROM diagnostics are active, the OS ROM that has
>that piece of code is $4000 area similar to the way ram banks are switched
>in & out. How it's called once it gets there, i.e. JSR $4000 or JMP $4000
>or JMP $???? I don't know. Ditto for the PBI stuff. The bright side is

<and more deletions>

Looking at the 800XL prints, and being a hardware kinda guy, I
might suggest pulling the PAL and putting it on a solderless
breadboard. turning the PB7 input on, and seeing which address
lines trigger the OS ROM output.  You would also have to simulate
the other inputs properly, such as pulling REFbar high, and the
other PBx inputs.

--
Richard Dell

 
 
 

1. XL/XE Diag rom mapping?

PlAnother stupid question, can anybody tell me precisely what the effect
Plon the memory mapping is when you turn on the 'enable diagnostic ROM' bit
Plon PB7.

The xl rom that is normally at $D000 to $D7FF (unused because that is where
the i/o chip addresses are) is switched down to $5000 to $57FF. This is done
by the pal chip in the xl/xe.

PlI've just discovered (after about 1 1/2 years!) that if you type 'BYE' on
Plmy modified 800 the system crashes :(.  The ROM image looks OK, so I
Plthink the decode logic must be confused.

 How can it be confused??  the decode logic is not there in the 800. Your xl
rom MUST be modified. The XL rom checks it self out at power up including
the self test rom which is not there. If it does not check out, the computer
jumps to the self test if it can.
   I have made a modified xl rom my self for the 800. I had 2 types. one
slightly modified so it would power up properly and one heavily modified to
include the soft reset, the memo pad (called it the XL MEMO PAD MODE) ,all 4
joysticks and 8 paddles. Unfortunately, i lost the files and will have to do
it again. I even had a board that had 16k on it to emulate  the ram under
the roms on an xl and when combined with the axalon ramdisk compatible board
i sell, a 130xe could be emulated (with out the antic bank switching).

  Tell me more about your 800!

 * Wave Rider 1.0 [NR] *
... UNREGISTERED EVALUATION COPY
--- Blue Wave/Maximus

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