CSC 340 Homework Assignment 4

Perform the indicated subtraction with the following unsigned binary numbers by taking the 2s complement of the subtrahend:

Problem#4.5 – Repeat problem 4, assuming the numbers are 2s complement signed numbers. Use extension to equalize the length of the operands. Indicate whether overflow occurs during the complement operations for any of the given subtrahends. Indicate whether overflow occurs overall for any of the given subtractions.

Problem#4.8 – Design two versions of the combinational circuit whose input is a 4-bit number and whose output is the 2s complement of the input number, for each of the following cases using AND,OR and Not gates:

The circuit is a simplified two-level circuit, plus inverters as needed for the input variables

(b) The circuit is made up of four identical two-input, two-output cells, one for each bit. The cells are connected in cascade, with lines similar to a carry between them. The value applied to the rightmost carry bit is 1.

(c) Calculate the gate input costs for the designs in (a) and (b) and determine which is the better design in terms of gate input cost.

Problem#4.11- Design a combinational circuit that compares two-4 bit unsigned numbers A and B to see whether B is greater than A. The circuit has one output X, so that X = 1 if A < B and X = 0 if A B.

Problem#4.16 – The adder-subtractor circuit of Figure 7 has the following values for input select S and data inputs A and B.