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Hi there,

Bit of a techie question here. I'm just wondering how the cartridges work - or to be specific, I'll give a theoretical example:

If I had a cartridge which offers nothing more than a few extra BASIC commands, how would this work? Would the cart identify itself as a disk controller and then in the $C002 initialisation routine extend the reserved word table etc? Or would you have an auto-starting (non-disk) cartridge that does the same thing then RTI/Reset?

Cheers.

If the Dragon (or CoCo) finds $444B ("DK") at $C000-$C001, it then jumps to the next location at $C002. If "DK" is not found, and the cartridge is wired to auto start, the interrupts are enabled and the FIRQ handler does a hardware init, clears the reset flag at $71, and jumps to $C000.

Cheers Zephyr, I think I'm slowly piecing this all together now.

Here are a couple of quick examples for you:

"DK" auto-start: FIRQ auto-start:

That's fantastic!!! Cheers mate - you are an absolute diamond.

Take a look at pages 238 to 242 of "Inside The Dragon" for a good example of adding new commands to BASIC.

Regards,
Steve

Unhelpfully, the Inside The Dragon book seems to have a typo - STUB2 hasn't been defined. I haven't had a chance to try and guess where it's supposed to go yet. Lol.

Cheers Steve.

If anyone is curious - I think
STUB2 EQU $0134
is the missing line.

Seemed to work... kinda. One of the two commands added in that example worked anyway.

Rink wrote:If anyone is curious - I think
STUB2 EQU $0134
is the missing line.

That is correct!

Rink wrote: Seemed to work... kinda. One of the two commands added in that example worked anyway.

You must have made a mistake somewhere because I typed in that example during the 80's and I clearly remember that both commands worked perfectly.

Cheers fella. I'll take another look shortly.