Binary parallel adder
- 3. Parallel Adder • A circuit , consisting of n full adders , that will add n-bit binary numbers. • The output consists of n sum bits and a carry bit. • CO of one full adder is connected to CI of the next full adder.
- 5. Serial Adder • The serial adder is a binary adder that is capable of forming sum and carry outputs for addend and augend words of greater than one bit in length.
- 7. Parallel & Serial Parallel • Faster. • It uses registers with parallel load capacity. • Number of full adder circuit is equal to number of bits in binary adder. • It is a combinational circuit. • Time required does not depend on the number of bits Serial • Slower • It uses shift registers. • It requires one full adder circuit. • It is sequential circuit. • Time required for addition depends on number of bits.
- 9. A binary parallel adder is a digital circuit that produces the arithmetic sum of two binary numbers in parallel.
- 10. STRUCTURE OF PARALLEL ADDER • Parallel adder nothing but a cascade of several full adders. • The number of full adders used will depend on the number of bits in the binary digits which require to be added.
- 11. DIFFERENT TYPES OF BINNER ADDER • ONE BIT PARALLEL ADDER • TWO BIT PARALLER ADDER • FOUR BIT PARALLER ADDER
- 12. BLOCK DIAGRAM OF ONE BIT PARALLEL ADDER
- 13. BLOCK DIAGRAM OF TWO-BIT PARALLEL ADDER
- 14. BLOCK DIAGRAM OF FOUR BIT PARALLEL ADDER
- 15. BLOCK DIAGRAM OF n-bit BINARY PARALLEL ADDER When an n-bit binary number is added to another , each column generates a sum and a 1 or 0 carry to the next higher order column.
- 16. For an example: A = 1011 B = 0011 S = 1110
- 17. Demonstration: subscript 4 3 2 1 Input carry 0 1 1 0 Ci Augend 1 0 1 1 Ai Addend 0 0 1 1 Bi Sum 1 1 1 0 Si Output carry 0 0 1 1 Ci+1
- 18. Procedure The bits are added with full-adder. Starting from the least significant position to form the sum and carry. The input carry CI1 in the least significant position must be zero. The value of CIi+1 in a given significant position is the output carry CO of the full adder. This value is transferred into the input carryCI of the full-adder that adds the bits one higher significant position to left. The sum bits are thus generated starting from the rightmost position and are available as soon as the corresponding previous carry bit is generated.
- 19. RIPPLE CARRY ADDER A binary parallel adder constructed this way is also called ripple carry adder as the carry output of each full-adder is connected to the carry input of the next higher-order stage.
- 20. Carry propagation delay • The sum and the output carry of any stage cannot be produced until the input carry occurs ,this causes a time delay, called the carry propagation delay • The carry propagation delay for each full- adder is the time from the application of the input carry until the output carry occurs, assuming that the A and B inputs are already present.
- 21. Worst case • The cumulative delay through all the adder stages is a “worst case” addition time. • The total delay can vary, depending on the carry bit produced by each full-adder.
- 22. IC •Several configuration of binary parallel adders are available in IC form. •Popular example:74283(4-bit binary parallel adder)
- 23. These parallel adders can be cascaded to form larger binary parallel adders. Eg: Two 7483 4-bit binary parallel adders can be cascaded by connecting the CO of the least significant adder to the CI of the next adder to form an 8-bit binary parallel adder