1.
Design Objects
Design
objects which are regularly used w.r.to design are design is explained below.
Design: {TOP, ENCODER,
REGFILE} Reference: {ENCODER, REGFILE, INV} Instance: {U1, U2, U3, U4}
Design
Design corresponds to the circuit description
that performs desired logical function. A design
consists of instances, nets, ports, and pins. It can contain subdesigns and
library cells.
Reference
This is the
original design to which the cell or instance refers. A reference is a library
component or design that can be used as an element in building a larger
circuit. The structure of the reference can be a simple logic gate or a more
complex design (a RAM core or CPU). A design can contain multiple occurrences
of a reference; each occurrence is an instance.
Instance
or Cell
An
instance is an occurrence in a circuit of a reference (a library component or
design) loaded in memory; each instance has a unique name. A design can contain
multiple instances; each instance points to the same reference but has a unique
name to distinguish it from other instances. An instance is also known as a
cell. A unique instance of a design within another design is called a
hierarchical instance. A unique instance of a library cell within a design is
called a leaf cell.
Ports
Ports are the inputs and outputs of a
design. The port direction is designated as input, output, or inout.
Pins
Pins are the input and output of cells
(such as gates and flip-flops) within a design. The ports of a subdesign are
pins within the parent design.
Nets
Nets are the wires that connect ports to
pins and pins to each other.
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