I am referring to the use of buffers when optos are not required, yet current limiting and rail clamping diodes are being suggested.

Rail clamping diodes will not keep the input within 0-vcc , and the resistor will slow the transition time. You would have to clamp to gnd + diode drop, and vcc - diode drop to keep a slow signal within the rails.

Plus, you have to guess when the 8052 really decides the input is 0 or 1. A buffer makes the decision for you, so you can see it going in. A buffer with hysteresis is even better.

If you destroy the buffer, you can easily replace it. If you destroy an 8052, you will have to hunt for a new one, program it, etc.


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