Re: Ultimax questions

From: Segher Boessenkool <>
Date: Thu, 10 May 2012 00:21:45 +0200
Message-Id: <>
>>> no, only on reads (except in ultimax mode). typically a cartridge  
>>> that
>>> wants to map ram to these areas will reconstruct the CS signal  
>>> from the
>>> adresslines and r/w.
>> Well, and in Ultimax mode?
> i am not sure to be honest, ultimax is a bit "special" =) i *think* it
> generates ROML/ROMH also for write accesses then.

Some time ago I decoded the PLA equations from a PLA dump (not the
one that is all over the web, because that one is corrupted).

Ultimax mode, that is:

not exrom and game:
0000..0fff, cpu: ram
8000..9fff, cpu: cartridge low
d000..dfff, (cpu read and ba) or cpu write: i/o
d000..dfff, cpu read and not ba: ram
e000..ffff, x1x, cpu: cartridge high
e000..ffff, x0x, cpu: ram

3000..3fff, 7000..7fff, b000..bfff, f000..ffff, vic: cartridge high
0000..0fff, vic: ram
8000..9fff, vic: ram
d000..efff, vic: ram
rest open bus

and the equations for #ROMH and #ROML are:

.11..100..010...  +.....+.
.....100..0.10..  +.....+.
         port x11, addr 100x, cpu read, exrom
         addr 100x, cpu, no exrom and game               -->  
cartridge low #CS

..1..101..0100..  +......+
.....111..0.10..  +......+
..........1.1011  +......+
         port x1x, addr 101x, cpu read, exrom and game
         port x1x, addr 111x, cpu, no exrom and game
         addr xx11, vic, no exrom and game               -->  
cartridge high #CS

So the only way to get #ROML for writes is in ultimax mode,
addr 8000..9fff; and to get #ROMH for writes, you need
ultimax mode, addr e000..ffff, and port 01 bit 1 high.


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Received on 2012-05-09 23:00:10

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