If you look closely at the picture of the keypad connector:



You will notice that it is an eight pin configuration. The 16 keys of this keypad will be organized into a matrix like showing in this typical 8051 MCU connection:



There is a posting here on the forum that shows how to structure code to read a keypad like this. You can read the original posting here:

Karas Key Pad Posting

If you look at the above posting and link through to the code you may find that the original code's tabbing looks a bit strange. The same code was reposted with the tabbing readjusted to make it look more readable here:

Andy's Repost of Code

That code is in C language. It should be quite easy to look at the code for concept and then write equivalent assembly code that does the same thing. You will learn a lot of things going through that exercise!! It is also possible to get the free eval copy of a C compiler, such as that offered by Keil, and make a small project that accepts the posted C code and compiles it. Upon completion of the compile look in the .LST file and you can see the compiler generated version of the assembler code.

Michael Karas