anakin@gpu.utcs.toronto.edu (Anakin Research) (01/21/89)
I have a fix for the LUCAS Micobotics problem that works on the only two amiga's I have to try it on. I make no guarantees but I'd like a couple of you out there to try it. The first thing that must be done is to build a terminator for the bus. Take an 86 pin female edge connector and put the following network on each of the 16 data lines and on *AS, *LDS, *UDS, & R/*W. That's 20 lines total. Data or Control line <------/\/\/\/\/\---------> 5 Volts + | 4.7K | | | | |----/\/\/\/\/\---| |---> Ground 1K | | 1000 pf. Next change U9 to a 74LS74 and change U8 to a straight 7474. I had a fix which involved using one type D pal, but I decided that it was such a hassle (and $20.00) to update people with a new pal, and there had to be a simpler method. I'm still not happy with this fix as it seems a little sensitive to me. Besides why should I have all the fun of finding this problem. Give it a try and let me know, don't be afraid to experiment. There seems to be some evidence that a fast memory access right after a *VMA and *VPA cycle could be a problem. Remember that because LUCAS is ASYNC. it is constantly delaying and speeding up to match up to the AMIGA 7M clock. I know making this terminator seems like alot of work but there are other advantages. One of my Amiga's doesn't like more than two peripherals on the bus, but with the terminator it can handle four. I've also had some success in operating LUCAS at 24 Meg with the terminator installed. True it is a little flakey at the moment but maybe I can make it more stable. By the way if anyone comes up with a more solid fix for the Microbotics memory board, that works across a fair number of 1000's, I will gladly send you a LUCAS board a PALS free. I'll keep trying for a better fix but I've got to get back to finishing the design on the 32_bit memory board. Good Luck ........ Brad BTW. The terminator idea was given to me by Jerry at Microbotics, Thanks