How fast can this type of resistive interface work?  Will it work for
frequencies up to 300kHz???
Or is there too much input capacitance to charge/discharge?
Dan



As I suggested earlier, "A 4049/4050 (Vdd=5V) will convert from the 4000
CMOS to PIC. (inverting / non-inverting hex buffer)" This works fast,
does 6 lines with a single part and uses almost zero power.

If you only have one or two lines you can either use a transistor or
resistor (preferably a resistor divider). Let's assume

Eg. 0/15V 4000 CMOS ----[22K]----x---------> To PIC
                                  |
                                 [10K]
                                  |
                                  0V

Note: This circuit should only be used with TTL-level PIC inputs, not
with Schmitt trigger CMOS level PIC inputs.

Using 4-resistor networks you can get 4 lines with two small parts.

Or get rid of the 10K resistor and depend on the PIC protection diode to
clamp the voltage, but this is not recommended in general- it could
cause a couple of subtle problems.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the
reward"
speff@interlog.com             Info for manufacturers:
http://www.trexon.com
Embedded software/hardware/analog  Info for designers:
http://www.speff.com

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