Registers
Registers are latches with some additional circuitry components to allow for some more control mechanisms. Usually this extra control is simply an enable signal, which can be activated or deactivated at the will of the controller. This means that the signals for a latch reset and set do not have to maintain a constantly correct or desirable signal, only when enable is activated do the data in those lines need to be correct.
class="normal">A few additional gates added to an SR latch in most cases achieve this. The SR latch consists of 2 NOR gates with one input of each connected to the output of the other, and the other inputs being SET and RESET lines for different signals. In this simple setup, if SET or RESET is set to a high voltage the output of the latch likely changes, making the necessity to maintain millions of different signal lines constant potentially. A register uses AND gates in front of each NOR gate which both have 1 enable input, and the other input is a SET and RESET. So no matter what the SET and RESET lines are currently at, it has no effect until the enable signal is high, and the AND gate can potentially pass a signal through. Registers are used all over in modern electronics, often in counting circuits and in memory and processor devices. Read more Read less