3. A digital circuit.
Sums the amplitudes of two input signals.
Representation of Adders:
Binary-Coded-Decimal or Excess-3
Processor Use:
Calculate addresses, table indices and
similar operations.
What is ADDER ?
5. Half ADDER:
A computational device.
Adds two binary digits .
No carry as input.
Produces a sum bit and
a carry bit.
Types of Adder
INPUTS OUTPUTS
A B SUM CARRY
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
Half Adder Circuit
6. Full Adder:
A computational device.
Adds three one-bit binary numbers.
Produces a sum of two inputs and a carry value.
Types of ADDER (Cont...)
INPUTS OUTPUTS
A B CIN COUT S
0 0 0 0 0
0 0 1 0 1
0 1 0 0 1
0 1 1 1 0
1 0 0 0 1
1 0 1 1 0
1 1 0 1 0
1 1 1 1 1
Full Adder Circuit
7. Also Known as 8421 digit.
A 4-bit binary adder.
Adds two 4-bit digits having a BCD.
Resulting format 4-bit output digit.
Sum exceeding decimal value of 9, a carry’s
generated.
What is BCD ADDER?
8. Conversion and Coding
(12)10
1100 00010010Conversion
Coding
(using BCD code
for each digit)
9. A 4-bit BCD code’s used to represent 0 to 9 digits.
Adding BCD numbers using BCD addition.
Adding 6 with the sum while exceeding 9 and generating a carry.
By adding 6 to the sum, make an invalid digit valid.
.
10. Maximum sum is 9+9 + 1 = 19
Max digit Carry from previous digits
14. If sum is up to 9
Use the regular Adder.
If the sum > 9
Use the regular adder and add 6 to the result
15. Sum of two BCD digits exceeding 9.
A carry is generated.
Converting the invalid digit into valid digit.
Carry generated by adding 6 to the invalid BCD digit’s
passed on to the next BCD digit.