Single step execution of Program

Hello all,

Well is it possible to execute a program residing inside 89c5x to be executed in single steps with the help of a key.That is when the key is pressed only one is executed.
Ex Prg:

Addr    mov a,#23H
Addr+2  anl a,#0f0H
Addr+2  mov 0f0h,a
Addr+1  .
...so on

Execution of the program at route assembly level happens at one instruction at a time.
Suggest how can it be done.

with regards
Abhinav.