cheesestraws
Well-known member
Perhaps a silly question - is the reset signal working?
The problem could be that RESET is not held for long enough for the processor's internal state to stabilize. According to the MC68000 User's Manual, page 10-12, note 4: "For power-up, the MC68000 must be held in the reset state for 100 ms to allow stabilization of on-chip circuitry. After the system is powered up, #56 refers to the minimum pulse width required to reset the processor."I checked the presence of the RESET and HALT signals - both are pulled HIGH, although i was measuring from the SWIM Chip socket, and although it was high, it looked like it was dipping for exactly 1 clock cycle to ground, then back to being pulled high.
The problem could be that RESET is not held for long enough for the processor's internal state to stabilize.
Pretty sure I mentioned that it was a Clock Signal Issue in My Prior Post... JS...Well, i was a very lucky boy for Christmas and santa brought me a new DS1102 Oscilloscope! Along with a Yihua 959D Hot Air station - I've just bought a Meanwell RT65B which has all the right voltages with enough current to set this up as a bench PSU for the board. I can monitor the video out signal on the scope. I tried in a separate SE/30 chassis but still no dice. I'm not getting anything. I think @techknight is right - there's a clock signal missing or not quite right somewhere.
Our very own @ScutBoy happens to volunteer there and if the other individual doesn't snatch up this machine I'll see if he can help us out. I think with the PLCC 84 breakout board designed by @Kai Robinson I'm building, it should be able to be cloned. I suspect the PDS card is also part of the system but that (should) be easy to do unless it has PAL in which case I'd have to send those out for to be reverse engineered.@maceffects
These folks seem to have one. Anyone live close? Do you think they'd let someone borrow it?
https://www.freegeektwincities.org/
Our very own @ScutBoy happens to volunteer there and if the other individual doesn't snatch up this machine I'll see if he can help us out. I think with the PLCC 84 breakout board designed by @Kai Robinson I'm building, it should be able to be cloned. I suspect the PDS card is also part of the system but that (should) be easy to do unless it has PAL in which case I'd have to send those out for to be reverse engineered.