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Implementation Details
5-65
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cmm_func iport(int x); // read a port
int i,j,k,l; // various temp and loop variables
int x[4]; // array holding the correct key sequence
int locked=1; //variable returned by lock()
cmm_func lock(){
x[0]= 0xEF; //MS7
x[1]= 0xBF; //MS9
x[2]= 0xEF; //MS7
x[3]= 0x7F; //MS10
locked=0;
cport(’B’, 0xFF); //Configure port B as output.
//Port B is the LED’s on the
//code development unit.
oport(’B’, 0xFF); //Turn off all 4 LEDs.
for (i=0; i<4; i++){ // loop through all required inputs
k=iport(’F’); // read port F
while( k == 0xFF ){ // wait for keypress
k=iport(’F’); // read port F
oport(’B’, k); // output the value from F
wait(100); // delay 100ms for key debouncing
}
l=iport(’F’); // read port F
while( l != 0xFF ){ // wait for key release
wait(100); // delay 100ms for key debouncing
l=iport(’F’); // read port F
}
if (x[i] != k) { // compare to correct input
locked=1; // if incorrect then lock and return
return locked;
}
} // end for (i=0; i<4; i++){
return locked; // If the program reaches this return then all inputs were
correct
// and the main program can unlock.
}
cmm_func main() // code begins executing here after init614.asm is executed
{
asminit(); // configure everything
cport(’B’, 0xFF); //configure port B as output
for (j=0; j<1000; j++){ //semi–infinite loop
if (lock()){ // get input and see if correct
// if lock()==1 the input was incorrect
// The LED’s are then flashed and the program repeats.
oport(’B’, 0x00);
wait(100);
oport(’B’, 0xFF);
wait(100);
oport(’B’, 0x00);
wait(100);
oport(’B’, 0xFF);