open-drain/open collector type of output

Why don't working this bus-selector?

MAX3000A (EPM3032A or EPM3064A).

Lines of both bus is pulluped by resistors 10K to VCC (+5).

After several tries, you finally succeded in showing an (almost) readable schematic.

But what's not working?

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After several tries, you finally succeded in showing an (almost) readable schematic.

But what's not working?

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In the simulator all ok.

Also I tryed add LCELL to adjust time-through of selection (see picture).

Real 74LS245 is working. But this schematic inside EPM3064A in same hardware don't working :-(.

What values of external pullups resistors is recomended?

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But this schematic inside EPM3064A in same hardware don't working :-(.

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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.

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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.

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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.

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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.

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By the way, when I looking buses with the connected selector (EPM3064A) by oscilloscope, I'm visually see differents on both sides (data-bus in CPU side, & data-bus in common-bus side).

On the CPU<->EPM3064A side it's look (compared with side CPU-common bus) too tightened, when lelel goes from logic-zero to logic-one.

I hope it is because of too high resistance of pullups resistors. I try to reduse resistance of it.

The Z80 busses I'm aware of, e.g. ECB don't use open collector data lines. ECB has LS245 type tri-state drivers. In so far there's no problem of too high pull-up resistance values. Of course, open collector can work for rather slow (a few MHz) busses, but I would expect 470 ohm to 1k pull-up level.

The drawback with open collector drivers is, that a sufficient current strength is required for all bus members, so you surely can't operate an unbuffered CMOS or MOS peripheral, which can still work with a not to heavily loaded tri-state bus.