sequential circuit with d flip flop

Projects General Guidance
1

my truth table for this circuit:

ABX|AB

000 00

001 01

010 01

011 10

100 10

101 11

110 11

111 00

my code:

//x=pin 8 and clk=pin 9, A=pin 6 and B=pin 7 clk=pin 2

int a,b,c,d,e,f,g,h,i,j,k,x;
int A,B;
int clk;

void setup(){
A=0;
B=0;

pinMode(6,OUTPUT);
pinMode(7, OUTPUT);
digitalWrite(6,LOW);
digitalWrite(7,LOW);
//delay(3000);
// attachInterrupt(0,clock,RISING);

}

void loop(){
x=digitalRead(8);
// clk=digitalRead(9);
a=NAND(b,c);
b=NOR(d,d);
c=NAND(x,g);
d=NAND(e,f);
e=NAND(A,h);
f=NAND(A,!B);
g=NAND(A,!B);
h=NOR(x,x);
i=NAND(h,B);
j=NAND(x,!B);
k=NAND(i,j);
int lasttemp =0;
int temp = digitalRead(9); // gets the clock pulse
delay(50);
if ( (temp != lasttemp) && (temp == 1) && clk!=1) {
A=dff(a,clk,A);
B=dff(k,clk,B);
clk =1;
}
else if (digitalRead(9)==0)clk = 0;
lasttemp=temp;

if(clk){

}
digitalWrite(6,A);
digitalWrite(7,B);
}

int NAND(int x, int y){
if(x && y)
return(0);
else return(1);
}

int NOR(int x, int y){
if(!x && !y)
return(1);
else return(0);
}

int dff(int d, int clk, int memory){
if (clk==1)
return(d);
else return(memory);
}

void clock(){
//int a,b,c,d,e,f,g,h,i,j,k,x;
//clk=digitalRead(9);
// x=digitalRead(8);
/*
int temp = digitalRead(9); // gets the clock pulse
delay(50);
if ( (temp != lasttemp) && (temp == 1) ) clk = 1;
else clk = 0;
lasttemp=temp;

*/
}

you can probably see that I am attempting to fix the button bounce. I always have problems with my code in the A output especially the first 3 rows of the truth table. My question is can you fix my code to do what I want it to. I have played with the idea of button debounce and attachInterupt as well. I am at a loss, also I have been thinking that there is a problem with the rising edge of my switches, i don't understand how to fix this

2 
if(clk){


}

What were you trying to accomplish here?

ortonjon:
x=digitalRead(8);

I doubt you're going to be able to read a smiley face with much success. (This is what the CODE tags are there for).

ortonjon:
can you fix my code to do what I want it to.

When is our assignment due by?

3

yeah sorry about the smilies and im not sure what you mean about when our assignment is due

4

ortonjon:
yeah sorry about the smilies

Not sorry enough to fix it, though, I guess.

and im not sure what you mean about when our assignment is due

Rather than asking for help, you asked us to do the work. I just wanted to know when we had to do it by.

5

Go back to your first post. Hit the modify icon.
Select the code, hit the # icon and then save it.

Why are you bothering to write all that logic simulation code?
The whole thing is simply a look up table. Two lines of code at the most.

Unless as was said it is an assignment from a class that you want us to do for you.

Why the title? The question has nothing to do with a sequential circuit or a d type flip flop unless you are holding back on more stuff as well.

6

jon,

I know that you're trying to build a structural model of the circuit, but I realized that the behavioral model is fairly easy to build.
I'll post the structural model in VHDL when I get the chance, but it may be a bit more work to model the circuit in C++.

/* Truth Table
    PS  | NS
    ---------
    ABx | AB
    ---------
    000 | 00
    001 | 01
    010 | 01
    011 | 10
    100 | 10
    101 | 11
    110 | 11
    111 | 00
*/

// I/O Pins:
// clock input is interrupt0 on pin 2
#define x 3 // x input on pin 3
#define A 4 // Flip-Flop A output on pin 4
#define B 5 // Flip-Flop B output on pin 5
boolean flag(0);
byte AB (B00); // initialize output of ffa & ffb to zero
//B00 means binary 00, for example B0101 = 5

void setup(){
    pinMode(3,INPUT);  // x
    pinMode(4,OUTPUT); // A
    pinMode(5,OUTPUT); // B
    attachInterrupt(0,trigger,RISING);
}

void loop(){
/* Write the outputs for ffa & ffb
   using the value from AB: bit 0 holds the value for B
   and bit 1 holds the value for A
*/   
  digitalWrite(A,bitRead(AB,1));
  digitalWrite(B,bitRead(AB,0));
  if (flag) {
    delay(250); // delay to debounce the switch
    flag--;     // reset the trigger to catch the next clock
    if (digitalRead(3)==1) AB = ++AB % 4;
/*
   no output changes unless x=1
   notice that the next state for AB is always
   one more than the current state, but never more than three
*/    
  }
}

void trigger(){
// update the trigger  
  if(!flag)flag++;
}