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4 bit binary Adder introduction:-
Binary adders are implemented to add two binary numbers of any length. To add two 4 bit binary numbers we need 4 bit binary adder.
Binary adders are implemented using full-adder connected in series as shown in block diagram below.
In this implementation Carry of each full-adder is connected to previous carry.
Binary adders are implemented using full-
In this implementation Carry of each full-
Example
Lets discuss one example for 4 bit binary Adder. In this example we will use some terms from Register Transfer Level (RTL) implementations.
Q. Add two binary numbers 7 and 15 with previous carry = 0.
Sol. Load the values in two registers R1 and R2.
So, R1 = 7 (decimal) = 0111 (in binary A3A2A1A0)
& R2 = 15 (decimal) = 1111 (in binary B3B2B1B0)
So from the above implementation we have -
Lets discuss one example for 4 bit binary Adder. In this example we will use some terms from Register Transfer Level (RTL) implementations.
Q. Add two binary numbers 7 and 15 with previous carry = 0.
Sol. Load the values in two registers R1 and R2.
So, R1 = 7 (decimal) = 0111 (in binary A3A2A1A0)
& R2 = 15 (decimal) = 1111 (in binary B3B2B1B0)
So from the above implementation we have -
Stage
Previous carry
Augends bits A
Addend bits B
Sum
Next carry
0
C0=0
A0=1
B0=1
S0=0
C1=1
1
C1=1
A1=1
B1=1
S1=1
C2=1
2
C2=1
A2=1
B2=1
S2=1
C3=1
3
C3=1
A3=0
B3=1
S3=0
C4=1
Sum of two binary numbers 7 and 15 from above table
Is C4S3S2S1S0 = 10110 (In Binary) = 16 (decimal)
Is C4S3S2S1S0 = 10110 (In Binary) = 16 (decimal)
In the results we have appended C4 in front of the sum digits to accommodate overflow bit from the binary addition flow. Overflow is discussed in this section.
Half-Adder , Full-Adder , Adder-Subtractor .
Verilog code - Half-Adder , Full-Adder
Verilog code -
Resources
Digital design resources
Clock Domain Crossing rtl & testbench.
Rate change (asynchronous) FIFO design and fifo depth calculation.
Half-adder , Full-adder , 4-bit binary adder , adder-subtractor circuit, overflow with rtl & testbench. Binary Multiplier, Parity error TT, Arithmetic, logical, shift micro-operations . Stack organization, LIFO, RPN discussion.
RTL coding guidelines. ICG cell, Assertions, $assertkill, levels.
Digital design Interview questions.
FPGA Interview. FPGA flow.
Guide to Graduate studies in US
Pipeline vs. Parallel processing.
Digital design resources
Clock Domain Crossing rtl & testbench.
Rate change (asynchronous) FIFO design and fifo depth calculation.
Half-
Digital design Interview questions.
FPGA Interview. FPGA flow.
Guide to Graduate studies in US
Pipeline vs. Parallel processing.