A one-way road meets a two-way road, as shown in Figure P8.25. The vehicles on the one-way road are allowed to make right turns and left turns only (i.e., it is a dead end). There are sensors to detect vehicles at positions A, B, and C, which generate high signals (logic-1) when vehicles are present and low signals (logic-0) when vehicles are not present. Logic hardware devices are to be developed to operate the right-turn signal (with active-high output R) and the left-turn signal (with active-high output L) in the one-way road. Inputs to these devices are the logic signals denoted by A, B, and C, as generated by the vehicle-detection sensors.

The logic governing the operation of the two signals is as follows: The right-turn signal is on when there are no vehicles at A and there are vehicles at C. The right-turn signal is on as well, when there are no vehicles at A, B, and C. The left-turn signal is on when there are no vehicles at A and B and there are vehicles at C.

(a) Express the logic governing the two devices

(b) Using a K-map, minimize the logic, if possible (c) Give circuits for implementing the two devices using NOR gates and NOT gates only

Figure P8.25