--- Quote Start ---
You're talking in riddles. I assume, that the
schematic as such is working, but possibly the part isn't behaving as expected with the external circuitry.
Real 74LS245 hasn't open drain outputs, so it can't behave identically. Actually, I don't understand why you are using open drain at all? For the same reason, I can't recommend a pull-up value.
--- Quote End ---
I build the upgrade-like device (inside EPM3064A) for old hardware computer (Z80A).
This device add some necessary fuction inside system.
But. To avoid conflicts with the existing in the common to all bus, I try to select CPU's bus.
In normal working it's simple bidirectional buffer (CPU<-BUS or BUS->CPU), when activated /BUSAK (CPU free the bus for the requested for it device) necessary to make true Z-state between bus of CPU & common for all BUS.
In some special cases EPM3064A must switch off common BUS, select CPU's bus only between internal port's device inside EPM3064A & CPU.
So. Really necessary in both sides of EPM3064A make true pulluped bus (beacose common Bus already pulluped (by 10K resistors). CPU's bus also have the opencollectors outputs & must to be pulluped.
Honored Contributor
