Microcontroller and IC(HCT,4000...) connection.Over current, ESD, EMI prevention

[Eh_Ba]

Hi
Is it necessary or preferred to place a resistor between Microcontroller (esp. PIC family) and IC(7400, 4000, darlington etc.) or not. If yes, how much ohm is good?

The HC(T) IC family has a 100 ohm resistor right between it's input pin and it's internal circuit and Darlington array IC's have such resistor.(e.g. ULN2803 have a 2.7 Kohm)
But is that internal resistor enough to prevent "over current" driven from micro's output pin or any harm made by EMI, ESD to both micro and ic, specially in harsh environment?(in case the micro's pin output signal to IC's input)

And what about the time, IC's (e.g 74HCT14) output is connected to micro's input pin. Do we have need to use resistor between them?

Sorry if my English is not good.
Thank you

 

[barry]

As long as the output of the micro doesn't exceed the maximum input voltage specification of the other IC, you should be fine.

 

[Eh_Ba]

Thank you Barry

 

[Eh_Ba]

A useful pdf about CMOS TTL interfacing.
**broken link removed**