Homework 3. Due October 10, 2001

Show the contents of A as requested below, given the circuit shown in the figure. 
Refer to AT89 series hardware description section on Port Structure and Operations.

MOV    A,  #FFh         ;  A =  ? 
MOV    P1, A;           ;  
MOV    A,  P1           ; A =  ? (explain)
XRL    P1, A;           ;
MOV    A,  P1           ; A =  ? (explain)

Is this circuit safe for the 8051? Explain your answers.