my supervisor wanted to add this diagnosis feature but he wasnt percise about any details, so i thought that i would make routine at the start which o/p's a constant value for ex: "11001100" on port 1(the one that takes the ADC o/p) and put a buffer that i control its selection and take the o/p of that buffer and connect it to all 4 digital i/p's, then select each i/p and compare what comes on port zero to what ive sent, but i still havent figured out how to test the analog i/p's, and im not sure weather this is gonna workout.

as for the indication i thought about using a shift register as u suggested.

i also thought that insterad of using the buffer and port 1, i'd use 2 cascaded shift registers (4094) as i saw on the site and use the first one for the indication and the second for the diagnosis. but still im not sure about any of these methods and none of them tests the analog i/p's...
any ideas??

by the way that 4094 chip has an o/p enable pin,, which i saw nothing about it in the diagram or the code on http://www.8052.com/users/garypeek/ what should i do with it, should i just connect it to the vcc??