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Sunday 9 September 2012

Module Path Declaration

Formal Definition

Module path declaration is used to describe how data can propagate through a module.

Simplified Syntax

Simple module path ;

Edge sensitive path ;

State dependent path ;


Let's take a look at this model:


The problem is to define delays between input and output (Y and A for example). The solution is to declare a path and specify a delay. There are three ways to do this:

· Declare a simple module path

· Edge a sensitive path

· State a dependent path.

The idea is to define the delay from the source to the destination. In this method each path can have a specific delay difference. For example, the path between Y and A can be different than Y and B. Generally, if a delay is specified, we know when the response occurs on the output if the input changes.

Examples of module path declarations are also described in chapters: Edge sensitive path, and State dependent path.


Simple module path example:

(A => Q) = 10;
(B => Q) = (12);
(C, D *> Q) = 18;

The symbols *> and => each represent a different kind of connection between the module path source and the module path destination. The operator *> establishes a full connection between source and destination. The operator => establishes a parallel connection between source and destination. Refer to the Language Reference Manual for a description of full connection and parallel connection paths.

Important Notes

· Module paths cannot be declared outside of a module.

· Only the net type of a port can be used as a source. Input and inout directions are allowed.

· Both registers and net types can be used as path destinations. Input and inout directions are allowed.

· A destination cannot have more than one driver.

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