Microcontrollers often have a very limited number of GPIO pins. Parallel-in serial-out shift registers can be used to read in a large number of input signals while only utilizing a few GPIO pins from the controller.

See more about this use case in the Logic Minute video Increase the Number of Inputs on a Microcontroller.

• The clock input controls the rate at which data is read out of the shift register
• The clock (F_clk) must be faster than the parallel input data (BR_in) based on the number of input bits (N) by this equation: F_clk (MHz) = BR_in (Mbps) × N
• For more inputs, shift registers can be daisy-chained together
• [FAQ] What is the default output of a latched device? (Flip-Flop, latch, register)
• [FAQ] Where do I find maximum power dissipation for a device?
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