Traffic light controller Consider the traffic light controller presented in Example 17.4.

1. Verify that the 2-out-of-4 coding allows to code the 5 internal states of the state graph.

2. Continue the coding of these states in order to obtain the logical expressions controlling the D inputs of the state synchronous D-flipflops.

3. Verify that every single stuck-at fault leads the circuit into one ofthe two 'safe' internal states: 'all flip-flops at 0' or 'all flip-flops at l' . Verify also that these two states are states from which one cannot exit.
4. What is the influence of a fault affecting the Clock?
5. Start the preceding study again with another coding of the internal states, for example a l-out-of-n coding.