380Z – Hmmm

The 380Z seems to be my system of the month and is causing me head scratching. It’s becoming one of those puzzles where you have to slide pieces around but you can’t because something is always blocking them.

 

Memory

I have tried moving the DRAMs on the CPU card around by one socket. I’m not sure that this made any tangiable difference. The screen rubbish doesn’t have as many ‘C’s and ‘0’s in it but left long enough it changes anyway. Did it allways do that? Not sure.

I would really like to read the EPROMS but they’re TMS2716s and they are different to the run of the mill 2716s and so the EPROM programmer I was kindly lent by a friend won’t ready them without an adapter, which we don’t have.

 

Defying logic.

I have borrowed a logic analyser in an attempt to see what’s going on on the bus. As I mentioned before, in a previous post, the bus terminator card has a row of holes and each signal is brought out to one of them. I have soldered some header pins so I can pop the wires of the logic probe on to key sognals and see what’s going on.

The short answer is nothing. nada, nilque. The long answer is that the logic analyser isn’t playing ball. If I use the ‘scope I can see a clock, memory requests, M1 bipping up and down, activity on the data bus, _RD_ is low and the first eight or so lines on the address bus are wibbling as expected. It’s frustrating the analyser won’t work as that would be a great help.