module Z74X163 
title '4-bit Binary Counter' 

" Input pins 
CLK, !LD, !CLR, ENP, ENT        pin; 
A, B, C, D                      pin; 

" Output pins 
QA, QB, QC, QD                  pin istype 'reg';
RCO                             pin istype 'com';

" Set definitions 
INPUT = [D, C, B, A]; 
COUNT = [QD, QC, QB, QA];

equations

COUNT.CLK = CLK;

COUNT := !CLR & ( LD & INPUT
                # !LD & (ENT & ENP) & (COUNT + 1)
                # !LD & !(ENT & ENP) & COUNT);

RCO = (COUNT == [1,1,1,1]) & ENT;

end Z74X163