The ripple-carry adder architecture suggested in the Design Problem uses 32 copi

Question

The ripple-carry adder architecture suggested in the Design Problem uses 32 copies of the full adder module to create a 32-bit adder. Each full adder has 3 inputs (A, B, CI) and two outputs (S, CO):

A single test vector for the full adder consists of 3 input values (one each for A, B and CI) and 2 output values (S and CO). To run a test the input values from the current test vector are applied to the device under test and then the actual output values are compared against the expected values listed by the test vector. This process is repeated until all the test vectors have been used. Assuming we know nothing about the internal circuitry of the full adder, how many test vectors would we need to exhaustively test its functionality?

Number of test vectors to exhaustively test full adder:

Explanation / Answer

Given is full adder.

A full adder has 3 inputs(i.e., A,B,CI) and 2 outputs(S,CO).

To know the functionality of device, we need to check the outputs of full adder against the expected values.

For this, we should know all the test vectors.

The number of test vectors depends on the number of inputs.

For 'n' number of inputs, number of test vectors is 2n

Here, for full adder there are 3 inputs then number of test vectors is 23 = 8

These 8 test vecors are {000, 001, 010, 011, 100, 101, 110, 111}

Therefore, number of test vectors to exhaustively test full adder is '8'

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