More like mud than concrete....
First I programmed up a ROM with Neal's code designed to test IC25.
Code:
ld hl, 0xc000 ; status write
loop: ld (hl), a ; write
inc a
jr loop
I checked the outputs of IC25, pins 2,16,19 showed a square wave with some 'glitchiness'. On the others, a more sinusoidal waveform of a higher frequency.
I then programmed up a rom to test the dot clock e.g.
Code:
ld hl, 0xc000 ; status write
ld a, 0x02 ; crystal dot clock
ld (hl), a ; write
loop: jr loop
With the above code, it was necessary to reset the CPU many times (10+) before I saw pin 9 of IC25 go high and select the 16Mhz Xtal dot clock. This seems to be the case at each power up.
I have little idea of what this all means as yet....
Next up is to check the reset via port B3, the code I have to do this is as per John e.g.
Code:
loop: in a,($b3)
out ($b3),a
jr loop