[atari7800] Re: [personal] Re: AW: 7800 cartridge detection

This discussion got me thinking that I never actually looked at the PAL
BIOS disassembly. So i did a diassembly and have been trying to figure
out how it works. Here's what I have found so far..
 
The BIOS compares FE00-FE7F with FE80-FF00 and if they are the same, it
assumes there no cartridge and jumps to internal game. 
Next if checks the reset vector, and if it's $FFFF or $0000 then it
assumes there's no cartridge and jumps to the internal game.
 
It looks like it then checks $FFF8 and $FFF9 for a valid 7800 cartidge
header. If it's not valid it starts the cartridge in 2600 mode.
 
That's all I have been able to figure out so far.
 
Dan
 

-----Original Message-----
From: atari7800-bounce@xxxxxxxxxxxxx
[mailto:atari7800-bounce@xxxxxxxxxxxxx] On Behalf Of Kroko
Sent: Wednesday, August 10, 2005 5:18 PM
To: atari7800@xxxxxxxxxxxxx
Subject: [personal] [atari7800] Re: AW: 7800 cartridge detection


Do you know, how the 7800 detects if a valid cartridge is plugged in ?
 
----- Original Message ----- 

From: Matthias  <mailto:matthias@xxxxxxxxxxxx> Luedtke 
To: atari7800@xxxxxxxxxxxxx 
Sent: Wednesday, August 10, 2005 11:09 PM
Subject: [atari7800] AW: 7800 cartridge detection


If you have trouble with more than one cartridge than I guess your 7800
have a problem.

 


  _____  


Von: atari7800-bounce@xxxxxxxxxxxxx
[mailto:atari7800-bounce@xxxxxxxxxxxxx] Im Auftrag von Kroko
Gesendet: Mittwoch, 10. August 2005 21:16
An: atari7800@xxxxxxxxxxxxx
Betreff: [atari7800] 7800 cartridge detection

 

Hi !

 

I am having trouble with a 7800. How does the 7800 detect that a
cartridge

is plugged into its cartridge port ? It starts up the built in Asteroids
for some of

the cartridges I have here, even if they are plugged in ...

 

Is the 7800 faulty or the cartridges, or is this a common problem ?

 

Armin

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