Globally asynchronous locally synchronous
Encyclopedia
Globally asynchronous locally synchronous (GALS) is a circuit that consists of a set of locally synchronous modules communicating with each other via asynchronous wrappers. Advantages include lower power consumption and electromagnetic interference
(EMI). GALS is sometimes used in system-on-a-chip
(SoC).
GALS is a compromise between a completely synchronous system (a single clock domain, perhaps with clock gating
on some registers) and a completely asynchronous circuit
(every register can be considered its own independent clock domain).
Each synchronous subsystem ("clock domain") can run on its own independent clock frequency.
Electromagnetic interference
Electromagnetic interference is disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit...
(EMI). GALS is sometimes used in system-on-a-chip
System-on-a-chip
A system on a chip or system on chip is an integrated circuit that integrates all components of a computer or other electronic system into a single chip. It may contain digital, analog, mixed-signal, and often radio-frequency functions—all on a single chip substrate...
(SoC).
GALS is a compromise between a completely synchronous system (a single clock domain, perhaps with clock gating
Clock gating
Clock gating is a power-saving technique used in many synchronous circuits-Description:Clock gating is a popular technique used in many synchronous circuits for reducing dynamic power dissipation. Clock gating saves power by adding more logic to a circuit to prune the clock tree...
on some registers) and a completely asynchronous circuit
Asynchronous circuit
An asynchronous circuit is a circuit in which the parts are largely autonomous. They are not governed by a clock circuit or global clock signal, but instead need only wait for the signals that indicate completion of instructions and operations. These signals are specified by simple data transfer...
(every register can be considered its own independent clock domain).
Each synchronous subsystem ("clock domain") can run on its own independent clock frequency.
See also
- Asynchronous circuitAsynchronous circuitAn asynchronous circuit is a circuit in which the parts are largely autonomous. They are not governed by a clock circuit or global clock signal, but instead need only wait for the signals that indicate completion of instructions and operations. These signals are specified by simple data transfer...
- Asynchronous system
- clock domain crossingClock domain crossingA clock domain crossing , or simply clock crossing, is when a signal crosses from one clock domain into another. If a signal does not assert long enough and is not registered, it may appear asynchronous on the incoming clock boundary....
- SIGNAL (a dataflow-oriented synchronous language enabling multi-clock and GALS specifications)