The NES $($Nintendo Entertainment System$)$ game controller is essentially a shift register that loads the state of the $8$ buttons on the rising edge of the $$LATCH$$ signal and shifts the value out serially on the $$DATA$$ line with subsequent rising edges of $$PULSE$$ as shown in the timing diagram below. The data is easily read by the game processor with another shift register. The data is persistent at each transition, so each button value can be latched and shifted into a shift register on each falling edge of pulse. However, the first value must be latched in using the Latch signal instead of the Pulse signal. For example, the A button can be read on the falling edge of Latch, the B button can be read on the first falling edge of Pulse, the Select button read on the second falling edge of pulse and so on$.$