andRegister

AndRegister is an informal term that appears in various engineering texts and library documentation to describe a register whose update is controlled by an enable condition. It is not a formal standard, but it is used to convey the idea that the stored value changes only when a gating signal is asserted, effectively applying an and-like condition to the data path during a clocked update.

In hardware contexts, an andRegister typically refers to a register with an enable input. When the enable is active, a new value is captured; when the enable is inactive, the register preserves its current contents. Implementations vary: some designs gate the data path with the enable, while others gate the clock or use a multiplexer to select between the new value and the current state. The key property is that the stored value does not update unless the enable condition is met, providing a controlled, conditional storage mechanism within synchronous circuits.

In software contexts, the phrase may describe a stateful element or abstraction that only updates its stored value when a predicate or flag is true. It can appear in firmware, simulations, or hardware description language code as a pattern for conditional storage or state progression.

Variants and considerations include synchronous versus asynchronous enable, and the potential hazards of improper enable timing, which can cause glitches or unintended updates. Good practices emphasize clear separation of clocking, enable logic, and data paths, and often prefer explicit multiplexing or dedicated enable inputs over clock gating for reliability.

See also: flip-flop, register, enable signal, clock gating, latch, synchronous design.