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Digital Electronics
Example 7.1
For the half-adder circuit of Fig. 7.23(a), the inputs applied at A and B are as shown in Fig. 7.23(b).
Plot the corresponding SUM and CARRY outputs on the same scale.
Solution
The SUM and CARRY waveforms can be plotted from our knowledge of the truth table of the halfadder. All that we need to remember to solve this problem is that 0 + 0 yields a ‘0’ as the SUM output
and a ‘0’ as the CARRY. 0 + 1 or 1 + 0 yield ‘1’ as the SUM output and ‘0’ as the CARRY. 1 + 1
produces a ‘0’ as the SUM output and a ‘1’ as the CARRY. The output waveforms are as shown in
Fig. 7.24.
Half Adder
S
A
B
C
(a)
A
B
(b)
Figure 7.23 Example 7.1.
Sum-output
Carry-output
Figure 7.24 Solution to example 7.1.