Okay. Time for a recap.
Firstly a few answers.
floobydust wrote:
As for construction, build up the board and run a solid ground between all of the chips first, then add the 0.1 bypass caps to each chip, then connect a +5V power line to each chip. I'd also suggest taking a picture of this and posting it before going any further. Most of my early wire-wrap projects used some proto boards that had bus patterns which could be used for power distribution. I used them to to distribute the ground and +5V to each chip and ensured that I had a solid ground and voltage feed to every component that needed them before moving to the next stage of construction.
Hi Floobydust. You'll see a litte lower that it looks like I actually have it all wired fine (phew, I wasn't looking forward to having to have to own up to a simple wiring problem!). I am going to rebuild it anyway as I want to add a few things so I will
GARTHWILSON wrote:
1/20 of the current? It takes a time to charge up the parasitic capacitance. To go from, say, 1V to 3.5V (a 2.5V swing), if the current is 1mA average (much higher to start, but tapering off to near zero as it gets above 3V), charging up 30pF of capacitance would take 75ns, mostly added to the access time. The access time is specified for a 50pF load, but only to the time it reaches 2.4V which will be long before it reaches a valid CMOS logic '1' when the current has dropped off so severely at the VOH. So depending on the glue-logic speed, even at 1MHz I wouldn't rule out a chance that pull-up resistors could take care of it.
Garth/BillO
I can't say I fully understand your discussion but I am indeed using the Aliance AS6C62256. Are you saying that with the W65C02 and that memory the pull-up resistors will or won't (or might not) work?
Anyway, this "Rockwell R65C02" that I bought from eBay (that isn't one of those, I reckon its an NMOS 6502 since it draws 80mA - thanks BillO) makes things very, VERY much better. If I treat it as the NMOS part it works fully - well as much as I have tested it, which is running a memory test program for 12 hours and an interrupt driven clock ever since.
So, the current theory is that the TTL memory chip doesn't drive the CMOS WDC '02 properly seems to be true. The one fly in the ointment is that I did add pullup resistors and it didn't help hugely. Maybe I needed lower resistance ones. I used 2k2.I really would like to get this project working using the WDC '02, so my plan is to re-build on a Twin Industries single ground plane board with sockets for pull-up resistors. I will do as floobydust suggests and add power and bypass caps first. Does anyone have any further suggestions please?