Changing RESET key function on XL?

[Laemeur]

Is it possible to get the RESET key on the XL series computers to do anything other than reset the system? Trying to change the interrupt routine vectors at $E474 and $E477 with POKEs is apparently not possible. Can I get around that with ML, or am I just approaching this from the wrong direction entirely?

[Rybags]

Not really.

 

For starters, it's a hardware Reset, and not a function key.

A Reset also sets the PIA back to it's default ($FF) outputs on the PORTA/B. So, that means Basic Off, OS ROM On, so any RAM-based OS idea becomes kinda null.

 

A cartridge can get almost immediate control of the system if it's a "Diagnostic" type... some games are like that, e.g. Star Raiders. Disadvantage is that they then inherit a system where virtually no initialisation has taken place, e.g. no screen setup, most OS RAM not initialised yet.

 

For disk-based stuff, CASINI, DISKINI and DOSVEC are the best bets. ($02,03) if bit 2 of location 9=1, ($0C,D) if bit 1 of 9=1. DOSVEC is the last thing the OS will attempt to run if no cartridge is present - by default it will go to the Self-test/Memo pad routine.

[Laemeur]

Hmm. That's what I was starting to suspect.

 

Thanks very much for the comprehensive answer. I really appreciate it.

[Rybags]

I should have added - if you burned your own OS to Eprom, or had an AtariMax 32in1, then you could insert your own code... of course you then have something that's unique to whatever machine it's in though.

[Marius]

What you can do is making a custom routine, which will be started AFTER reset is pressed.

 

I think that is not what you want, but it is possible to start a custom routine after the OS reset routine.

[_The Doctor__]

Is it not possible to modify some of the translator disks to do this, as they replace the os and then vector jump to the new os in ram. A software version os swap as opposed to a chip swap. That might be where to start

 

What you can do is making a custom routine, which will be started AFTER reset is pressed.

 

I think that is not what you want, but it is possible to start a custom routine after the OS reset routine.

[Rybags]

The only options are the disk/tape init vectors, and DOSVEC.

 

All Translator does is use that method, switch the alternate OS in, then continue with the (alternate) warmstart code.

[_The Doctor__]

there is more than one translator type OS so I was thinking using the same method the code could be used to shoehorn something in there at the very least allowing the system to pick up exactly where it left off...

The only options are the disk/tape init vectors, and DOSVEC.

 

All Translator does is use that method, switch the alternate OS in, then continue with the (alternate) warmstart code.

[a8isa1]

Is it possible to get the RESET key on the XL series computers to do anything other than reset the system? Trying to change the interrupt routine vectors at $E474 and $E477 with POKEs is apparently not possible. Can I get around that with ML, or am I just approaching this from the wrong direction entirely?

Sounds like you can't get around this problem directly.

 

You could build a switch for the interupt line on the SIO port. The vector is VINTER ($204). Just change it to point to your routine.

 

I'm not 100% sure but I don't think any SIO devices currently available use the interupt line.

 

- Steve Sheppard

Edited January 26, 2009 by a8isa1

[atariksi]

Is it possible to get the RESET key on the XL series computers to do anything other than reset the system? Trying to change the interrupt routine vectors at $E474 and $E477 with POKEs is apparently not possible. Can I get around that with ML, or am I just approaching this from the wrong direction entirely?

Sounds like you can't get around this problem directly.

 

You could build a switch for the interupt line on the SIO port. The vector is VINTER ($204). Just change it to point to your routine.

 

I'm not 100% sure but I don't think any SIO devices currently available use the interupt line.

 

- Steve Sheppard

 

There's more control on the RESET on Atari 800 than XL/XE. What exactly does he want the RESET to do and is it time critical?