Simple Traffic Light Controller
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Inputs:
clk, reset
next
Outputs:
color (RED, YELLOW, GREEN)
Behavior:
On reset, the 'color' output is set to RED
After reset is deasserted, each 0->1 transition of 'next' results in the 'color' output to cycle through the sequence:
RED -> GREEN -> YELLOW -> RED -> GREEN -> YELLOW .....
