Chip name: FullSubtractor
Inputs: a, b, c
Outputs: diff, borrow
Function: diff = LSB of a - b - c
borrow = MSB of a - b - c
Abstraction of Full Subtractor Chip - Representation, Implementation and Truth Table
Implementation of Full Subtractor Chip in HDL
The function in the above abstraction can help in the implementation of Full Subtractor Chip.
diff = a XOR b XOR c
borrow = (a' AND b) OR (b AND c) OR (a' AND c)
CHIP FullSubtractor {
IN a, b, c; // 1-bit inputs
OUT diff, // Right bit of a + b + c
borrow; // Left bit of a + b + c
PARTS:
// Put you code here:
HalfSubtractor(a=a, b=b, diff=diffab, borrow=borrowab);
HalfSubtractor(a=diffab, b=c, diff=diff, borrow=temp);
Or(a=temp, b=borrowab, out=borrow);
}
Implementation of Full Subtractor Chip in Java™
Similar to the Implementation in HDL
package CombChips;
class FullSubtractor_Gate extends HalfSubtractor_Gate {
protected static int[] FullSubtractor(int a, int b, int c) {
int[] out = new int[2];
int[] ab = HalfSubtractor(a, b);
int[] temp = HalfSubtractor(ab[0], c);
int borrow = Or_Gate.Or(temp[1], ab[1]);
out[0] = temp[0];
out[1] = borrow;
return out;
}
}
