if the voltage on P0 was inadequate to drive a latch, what about that on P2? Did it work for some reason relating to the fact it was unbuffered? The reason I'm interested in this is that the DS89C4x0's have several address multiplexing modes, one of which (the default) is like the "standard" 805x, but the other two of which are quite different. The result is that I have, in one of my prototypes, three latches, and two '245 buffers, which provides the address latch function and the data bus buffering as well as the high-address buffer (more as a way to use the latch that would otherwise be in the way) so that my prototype can work in all available modes including the old standard.

What concerns me is that I want to use the same circuit, if possible, with standard parts, not necessarily the HMOS ones, but more modern DIP40 or PLCC44 parts, on the same board if it seems appropriate. If the latch on P2 will require the pullups as well, then I guess I'll provide for them.

I'm not excited about making up separate PCB's for each of several combinations of memory and MCU's, so I expect them all to live on the same PCB, perhaps with some options (jumpers, PLD, etc).

RE