It is necessary to design a digital circuit with four inputs C, S, Z, and V and 10 outputs, one for each of the branch conditions listed in Probs. 8-26 and 8-27. (The equal and unequal conditions are common to both tables.) Draw the logic diagram of the circuit using two OR gates, one XOR gate, and five inverters.

Prob. 8-26

Two unsigned numbers A and B are compared by subtracting A - B. The carry status bit is considered as a borrow bit after a compare instruction in most commercial computers, so that C = 1 if A

Prob. 8-27

Two signed numbers A and B represented in signed-2's complement form are compared by subtracting A - B. Status bits S, Z, and V are set or cleared depending on the result of the operation. (Note that there is a sign reversal if an overflow occurs.) Show that the relative magnitude of A and B can be determined from inspection of the status bits as specified below. (See also Table 8-11.)

Table 8-11

Transcribed Image Text:

Table for Problem 8-26 Relation A > B ΑΣ Β A