Hi,

Having just successfully built my SBC 2.3, I would like to make a few comments.

1) Thanks to Daryl for designing a great little board and producing from very nice PCBs.

2) I had two slight problems with my completed board. The first of these was that the 6551 clock crystal was not oscillating. I had built the board with a 33pF capacitor as being the closest to 30pF that I had to hand. On Daryl's suggestion I changed this to 22pF and the clock started running. The second problem is entirely due to laziness on my behalf which resulted in not getting a clean reset so the CPU was not starting.

3) For information, I'm using a W65C02 and a 6551 with a manufacturing code of 8409!

Again, I would like to express my thanks to Daryl for both producing the PCBs and for the help in getting it going.



Simon

Simon, have you considered using a clock oscillator instead of a crystal with capacitors? In a couple of year's time, caps tend to change value to the point where they can shut down the crystakl circuitry, or change value enough to get wierd responses. I used a 4 MHz oscillator on mine, and its running like a champ.

for the rest, you can always use the uP supervisory chips, but availability in the future may be an issue. I use an RC time constant. 10 uF cap, 10K resistor, I also use a diode across the resistor; banded end up at +5 volts. The resaon for this is that it shunts out the cap when the power goes down, ensuring a reset the next time round. I then buffer the reset through a 74LS04, and voila! the job is done!

_________________
"My biggest dream in life? Building black plywood Habitrails"

Tony,

Thanks for the tips - I'll bear them in mind for the future.

Regards,

Simon

I've updated my web site with the change of the 30pf capacitor with a 22pf one. While a 30pf might work for some, the 22pf part seems to work better. For reference, the 30pf value was taken from the CMD 6551 tech docs.

Thanks Simon!

Daryl