in fact it is a for substitute simulation 8870 using 8951 and keypad
    I made it according to the datasheet 8870
    P0.0 = Q0 p0.1=Q1 p0.2 = Q2 p0.3= Q3 p0.7=StD & p2.7 = TOE
    how it works is:
    * if button 1 is pressed then the data p.0.0-p0.3 = 0001
    * if button 2 is pressed then the data p.0.0-p0.3 = 0010
    * if button 3 is pressed then the data p.0.0-p0.3 = 0011
    * if button 4 is pressed then the data p.0.0-p0.3 = 0100
    so on until
    * if the 0 key is pressed then the data p.0-p0.3 = 1010
    any suppression issue StD pin high to low 1-->0
    and if given the TOE pin low then p.0.0-p0.3 will high all

    if there is an error please correct me this idea ..