[Rcxemul-discussion] Another update

[David E. <d.a...@du...>]

I know it was quick, but I decided to implement the interrupt for the
on/off switch. When the CPU hits the software sleep state (i.e. ROM has
finished initialising), I generate the interrupt. It then calls a bit of
code (looks like it tidies up the IRQ input) then returns to normal
program execution.

I've followed it through on Kekoa's ROM description and it's following
all the paths it should do. It's getting into the firmware update
function, and tomorrow I'm going to have a look at what's happening in
there. I presume if it's the first time the function has run, it will
wait for firmware to be downloaded.

Unfortunately this is going to make it more difficult to get a valid
firmware image in without using the serial port. The only way to do it
would be to go in and alter the memory to fool it into thinking that the
firmware has been downloaded.

On the bright side, if I had a sound module working, I'm pretty sure it
would have beeped twice! ;)