#88 AMX mouse

[Stuart Brady]

Apparently this is very good for high resolution displays, and I expect better in all sorts of ways than Kempston. It uses the Z80-SIO serial chip, and Andrew Owen suggests this could also be used for a more generic serial peripheral, so it would be best to keep this cleanly separated from the AMX-specific bits. There's a bit of software for this, but not a huge amount.

[Stuart Brady]

Correction: the AMX mouse interface uses Z80-PIO, not Z80-SIO.