On the left side, 5 inputs from top-left to bottom-left, data of bit1, data write, clock, data of bit2, data enable.
On the right side, top Led is bit 1, bottom led is bit 2.
Data Enable = 1, then no bit available on the output.
Data Enable = 0, display the current register value, whatever data bits values on the left.
A new value is set by data write = 1 AND clock = 1, then data bits are copied on the leds.
A new value can be set in register while data enable = 1, even if the leds are off. The set value will appear when data enable = 0
