Changes
Bryce.
:Yup, the original rate is unknown, so nobody could expect that you use the same rate :-) the [[AMX Mouse]] page includes a notice that the hardware is (likely) not producing exact 1/300s pulses. A similar notice on your page would be fine, at the moment it says 1/300s.
:The COM pin is low anytime when keyboard matrix row9 is selected, ie. anytime when reading from joystick (and possibly at times when not reading, but row9 still being selected). That's perfectly okay.
:The joysticks do have a pull-up (at the input side inside of the CPC) (for joysticks, COM is used only to drag-down that inputs).
:A more realistic worst-case: Say somebody reads mouse direction (COM=LOW), and immediately thereafter the scroll wheel (COM2=LOW). In that case you may have only 10-20 clock cycles, so COM would need to raise relative fast, else the 74LS240 would be still selected when reading the wheel. With pull-up it'd be be plenty of time, but if it gets pulled up "through the air" it could be a problem.
:Anyways, I haven't tried, so maybe there's no problem at all. Until some days ago I didn't even knew that COM and COM2 are open collector outputs, so I guessed many people could be trapped there, expecting stable HIGH levels on that pins. Ciao, --[[User:Nocash|Nocash]] 19:11, 18 April 2010 (UTC)
