Binary multipliers
- 1. SYED HASAN SAEED [email protected] [email protected] 1 SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW
- 2. BINARY MULTIPLIERS SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 2
- 3. BINARY MULTIPLIERS A Combinational multiplier is the logic circuit which is implemented to perform multiplication. The multiplicand is multiplied by each bit of the multiplier starting from the least significant bit. Each multiplication forms a partial product, successive partial products are shifted one position to the left. The final product is obtained from the sum of the partial products. SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 3
- 4. SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 4 2-bit by 2-bit Binary Multiplier: 2-Bit By 2-Bit Multiplier A B A1AO B1BO P=P3P2P1PO FIG. 1
- 5. (i) 2-bit by 2-bit Binary Multiplier: Consider the following multiplication of two 2-bit number B1 BO A1 AO Multiplier AOB1 AOBO A1B1 A1BO P3 P2 P1 PO PO = AOBO P1=AOB1+A1BO P2=A1B1+ C1 P3= C2 SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 5 Multiplicand Partial Product 1 Partial Product 2 C1 C1 C2 C2 X Final Result
- 6. IMPLEMENTATION OF GATES SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 6 AO BO PO BO A1 AO B1 A1 B1 P1 P2 P3C2= C1 A1BO AOB1 A1B1 HA HA PO = AOBO P1=AOB1+A1BO P2=A1B1+ C1 P3= C2 FIG. 2
- 7. Multiplicand Bits are B1 and BO, Multiplier bits are A1 and AO and the products is P3P2P1PO. First partial product is formed by multiplying BO by AO and B1 by AO Multiplication of AO and BO produces 1, if both bits are 1; otherwise it produces 0. This indicates an AND operation. Therefore partial product can be implemented with AND gates. The second partial product can be obtained by multiplying BO by A1 and B1 by A1 and shifted one position to the left. The two partial product are added with two half adder circuits. Usually there are more bits in the partial products and it is necessary to use full adder to produce the sum of partial products. 2-bit by 2-bit Binary Multiplier shown in fig.3 SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 7
- 8. SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 8 HA HA BOB1 BOB1 AO A1 Fig.3:2-Bitby2-BitBinaryMultiplier POP1P2P3
- 9. B3B2B1BO A2A1AO SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 9 AOB3 AOB2 AOB1 AOBO A1B3 A1B2 A1B1 A1BO (ii) 4-Bit By 3-Bit Binary Multiplier COC1C2 SOS1S2S3 A2B3 A2B2 A2B1 A2BO C3C4C5 S4S5S6C6 PO P1P2P3P4P5 P6 Multiplicand Multiplier Partial Product 1 Partial Product 2 Partial Sum 1 Partial Product 3 Partial Sum 2 Final Result
- 10. • The partial product terms are produced via bit by bit multiplication. This is equivalent to ANDing of two bits. • Finally the partial product terms in each column are added together to get final product terms. • No. of AND gates= m * n, where m= multiplier bits and n= multiplicand bits. • (m-1)n-bit adders required to produce a product of m+n bits. • For 4-bit by 3-bit multiplier, the no. of AND gates=3*4=12 • Two 4-bit adders are required to produce product of seven bits. • Fig. 2 shows the 4-bit by 3-bit multiplier. SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 10
- 11. (ii) 4-Bit By 3-Bit Binary Multiplier: SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 11 B2 B1 BOB3 BOB1B2B3 ADDEND AUGEND SUM AND OUTPUT CARRY ADDEND AUGEND SUM AND OUTPUT CARRY 4-BIT ADDER 4-BIT ADDER AO A1 A2 POP1 P2P3P4P5 P6 0 BOB1B2B3 AOBO AOB1 AOB2 AOB3 A1BO A1B1 A1B2 A1B3 AOB1 + A1BO SO FIG.4
- 12. (iii) 4- Bit By 4-Bit Binary Multiplier: It is a combinational circuit. This logic circuit is implemented to perform multiplication of two 4-bit binary numbers A= A3A2A1AO and B=B3B2B1BO A3 A2 A1 AO B3 B2 B1 BO SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 12 BOA3 BOA2 BOA1 BOAO B1A3 B1A2 B1A1 B1AO B2A3 B2A2 B2A1 B2AO B3A3 B3A2 B3A1 B3AO COC1C2 SOS1S2S3C3 C4C5C6 S4S5S6 S7C7 C8C9C10 S8S9S10S11C11 POP1P2P3P4P5P6P7 Multiplicand Multiplier Partial Product 1 Partial Product 2 Partial Product 3 Partial Sum 1 Partial Product 4 Partial Sum 2 Partial Sum 3 Final Result
- 13. In this process the first partial product is obtained by multiplying BO with A3A2A1AO , the second partial product is formed by multiplying B1 with A3A2A1AO , likewise for III and IV partial products. These partial products can be implemented with AND gates (as shown in fig.) These partial product are then added by using 4 bit parallel adder. The three most significant bits of first partial product with carry (considered as zero) are added with second partial term in first full adder. Then the result is added to the next partial product with carry out and it goes on till the final partial product, finally it produces 8 bit sum which indicates the multiplication of two binary numbers. SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 13
- 14. SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 14 A1 AOA2A3 A3 A2 A1 AO A3 A2 A1 AO A3 AOA1A2 BO B1 B3 B2 POP1P6 AOBO BOA1+B1AO P3P5 P2P7 P4 4- Bit Binary Adder 1 4- Bit Binary Adder 2 4- Bit Binary Adder 3 SOS1S2S3 Cout S4S5S6S7 Cout S8S9S10 S11 FIG.4:4-BitBy4-BitBinaryParallel Multiplier 0
- 15. References: • Digital Design, Pearson, 4th Edition. • Digital Circuit and Design, S. Salivahanan and S. Arivazhagan, Oxford University Press, 5th Edition. • Digital Systems Principles & Applications, Ronald J. Tocci, Prentice-Hall of India Pvt. Ltd. , 6th Edition. SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 15
- 16. THANK YOU SYED HASAN SAEED, INTEGRAL UNIVERSITY LUCKNOW 16