PPC MLDL

[hth]

I never heard of the PPC MLDL.

Back in the days I wired my own based on the design in a PPC Journal (Lynn Wilkins I believe).

I changed the design a bit to use a single 8K EPROM and read out 2 bits and latch, then read out the lower 8 bits. That gave me a single EPROM per 4K module (not the 4K + 2K variant). I also powered up the chip one cycle earlier with the hope it would ramp up power for working with my 2x speeded 41CV and it did.

The only problem I had was that it did not work first. A scope helped me show the problem. One of the signals had its spikes but also a tiny thin spike. That was the counter for 30. After some thinking I realized that when it wrapped from 39 to 40, it very briefly had 30 again, screwing everything up. The 10 and 1 counters are separate. I added one extra AND gate to only check that signal in the "middle", which sorted the problem.

I used wire wrap wire, but soldered directly on the chip legs, no sockets. That MLDL has a lot of wiring, supported 2 RAM pages and 4 EPROM pages. I used it for years without any problems and it probably still works. Power mileage was good too.

I bit-banged a serial port connected to the MLDL to download software to its RAM by simulating the 41 bus. The computer had one cable, the 41 one and the MLDL had a very nice quick release connector.

These days I use a simulator for most development, MLDL2000 for early testing and Clonix for production.