7 Jul
2014
7 Jul
'14
2:39 p.m.
On Mon, Jul 7, 2014 at 2:02 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Another
favourite trick was to use a spare channel on a Z80-CTC, pre-loaded with 1,
I hadn't thought to check for that. There is a Z80-CTC present.
How hard would it be to trace out the scheamtic sof
this [Quay MPS-90F]
board?
I've mostly been able to find other signals of interest using a Rho
Enterprises low-voltage continuity tester, without having to remove the
board from the machine. Removing the board is a hassle and the serial
daughtercard is soldered in place so I can't get to everything even if the
board is removed. The two big mysteries that I haven't resolved that way
are the FDC interrupt and the SIO clock.
The SIO clock situation is interesting because the SIO is on a daughtercard
that's soldered into a PIO footprint on the main board. There's no BRG on
the daughtercard, and no sign of rework on the main board to route CTC
outputs to that PIO footprint. Also the continuity tester didn't reveal
any connections between the main board CTC and the daughercard SIO clock
inputs.