Another GPIO question

GPIO Timing...

If I were to loop back one pin of say PortA to another pin of PortA, one set as output, the other input, how long will it take between setting the output pin and being able to read back the change on the input pin?

Certainly, if that loopback is an external device with a propagation delay of 140 nS, running the CPU at 6MHz, I will not see the input pin change for several CPU clocks...

Orin.