I'm getting confused by the datasheet for the Z84C00 CPU, while trying to work out if I can use it to drive 74HCxxx chips, or if I need TTL-compatible logic (i.e. either 74HCTxxx or 74LSxxx). It's clear that the low level voltages are compatible, but I can't work out what's going on with the high level voltages.
74HCxxx chips require between 3.15V (at VCC = 4.5V) and 4.2V (at VCC = 6V); I don't expect my voltage input to range this far (I plan on keeping it between 5.2V and 5.5V).
The output for the Z84C00 is specified in its datasheet (p34) as:
Symbol Parameter Min Max Unit Condition VOH1 Output High Voltage 2.4 V IOH = -1.6mA VOH2 Output High Voltage VCC-0.8 V IOH = -250uA
This seems to suggest that the voltage varies dependent on the input current on the pin, but isn't the input current entirely dependent on the internal circuitry of the chip itself? How can I work out what the expected voltage of the output will be?
I'm also not sure what the subscript "1" and "2" in the symbol name here is used for. I can't see any reference to them elsewhere, and the equivalent NMOS parts don't use the subscripts, just giving a single line (with 2.4V output level). How should I interpret this?