In electronic low power digital
synchronous circuit
In digital electronics, a synchronous circuit is a digital circuit in which the changes in the state of memory elements are synchronized by a clock signal. In a sequential digital logic circuit, data are stored in memory devices called flip-fl ...
design, operand isolation is a technique for minimizing the energy overhead associated with redundant operations by selectively blocking the propagation of
switching activity through the circuit.
"Overview of the power minimization techniques employed in the IBM PowerPC 4xx embedded controllers"
This technique isolates sections of the circuit (operation
Operation or Operations may refer to:
Arts, entertainment and media
* ''Operation'' (game), a battery-operated board game that challenges dexterity
* Operation (music), a term used in musical set theory
* ''Operations'' (magazine), Multi-Ma ...
) from "seeing" changes on their inputs (operands
In mathematics, an operand is the object of a mathematical operation, i.e., it is the object or quantity that is operated on.
Example
The following arithmetic expression shows an example of operators and operands:
:3 + 6 = 9
In the above exampl ...
) unless they are expected to respond to them.
This is usually done using latch
A latch or catch (called sneck in Northern England and Scotland) is a type of mechanical fastener that joins two (or more) objects or surfaces while allowing for their regular separation. A latch typically engages another piece of hardware on t ...
es at the inputs of the circuit. The latches become transparent only when the result of the operation is going to be used. One can also use multiplexers or simple AND gate
The AND gate is a basic digital logic gate that implements logical conjunction (∧) from mathematical logic AND gate behaves according to the truth table. A HIGH output (1) results only if all the inputs to the AND gate are HIGH (1). If not all ...
s instead of latches.
Overhead
There is some area overhead associated with this technique since the circuit designer needs to add extra circuitry, i.e. latches, at the inputs. Also, if the latches are being added in a pipeline
Pipeline may refer to:
Electronics, computers and computing
* Pipeline (computing), a chain of data-processing stages or a CPU optimization found on
** Instruction pipelining, a technique for implementing instruction-level parallelism within a s ...
stage, they might change the critical path, and hence increase the propagation delay
Propagation delay is the time duration taken for a signal to reach its destination. It can relate to networking, electronics or physics. ''Hold time'' is the minimum interval required for the logic level to remain on the input after triggering e ...
and cycle time. In cases where the overhead is not acceptable, one can think of clock gating
Clock gating is a popular technique used in many synchronous circuits for reducing dynamic power dissipation, by removing the clock signal when the circuit is not in use or ignores clock signal. Clock gating saves power by pruning the clock tree, ...
as an alternative method of low power design.
See also
* Glitch removal
Glitch removal is the elimination of glitchesunnecessary signal transitions without functionalityfrom electronic circuits. Power dissipation of a gate occurs in two ways: static power dissipation and dynamic power dissipation. Glitch power comes un ...
* Clock gating
Clock gating is a popular technique used in many synchronous circuits for reducing dynamic power dissipation, by removing the clock signal when the circuit is not in use or ignores clock signal. Clock gating saves power by pruning the clock tree, ...
* {{ill, Switching loss, lt=Switching losses, de, Schaltverluste
* Distributive law
In mathematics, the distributive property of binary operations generalizes the distributive law, which asserts that the equality
x \cdot (y + z) = x \cdot y + x \cdot z
is always true in elementary algebra.
For example, in elementary arithmetic, ...
- a similar idea in mathematics
* Reduction (mathematics)
In mathematics, reduction refers to the rewriting of an expression into a simpler form. For example, the process of rewriting a fraction into one with the smallest whole-number denominator possible (while keeping the numerator a whole number) is c ...
- a similar idea in mathematics
* Reducing a fraction
A fraction (from la, fractus, "broken") represents a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, a fraction describes how many parts of a certain size there are, for example, one-half, eight ...
- a similar idea in mathematics
* Reduced Karnaugh map
Logic optimization is a process of finding an equivalent representation of the specified logic circuit under one or more specified constraints. This process is a part of a logic synthesis applied in digital electronics and integrated circuit de ...
(RKM) - a similar technique in logic optimization
* Infrequent variables
Logic optimization is a process of finding an equivalent representation of the specified logic circuit under one or more specified constraints. This process is a part of a logic synthesis applied in digital electronics and integrated circuit de ...
- a similar technique in logic optimization
References
Electrical circuits