You haven't given us much information to work with on your question. Some information might be helpful.

List each input you will use with the following information...

1) Input type: Parallel, asynchronous serial, synchronous serial, binary (on/off), or protocol XYZ?

2) Hold time of the information. That is, how long is the input visible on the input pins?

3) What is the data transmission rate? How often does the data need to be read?

4) Required time to respond to the input before action must be taken.

Also, it is helpful to know the uP's speed, what other tasks are being performed in the uP, and how time critical are those tasks.

We can theorize about generalities, but you probably have some specific problem to work on which is much easier (and more fun) to respond to.

<>< Lance.