fordp wrote:Thanks for that Mark but are the physical mice Quadrature or some some other system?
The mice for all the 16/32 bit Atari systems (ST, STF, STM, STFM, Mega ST, Mega STE, Falcon and TT) are all quadrature mice. As are the mice for the Amiga, and for most ZX Spectrum and Amstrad CPC mouse interfaces. And of course most BBC B/Master systems.
Now, I don't know about the details for the Amiga. But the Atari, and most of the rest I listed use software to carry out the decoding. At least one interface for the Amstrad CPC used hardware (74LS series logic) to decode the quadrature mouse signals. It uses up/down counters. The Z80 MPU then reads the counter outputs (one for up/down and one for left/right).