I agree with kiran having provision for a PC PS/2 type keyboard will be certaintly great. Often it is needed to have more than those 16 keys and in such cases PS/2 is an excellent solution.

Interface is pretty simple only two port pins are required for interfacing CLK and DATA. A very small program is enough for interfacing. Infact it is easier to interface PS/2 than 16 key matrix.

Regards,
Prahlad Purohit