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Using latent state in circuits (Read 1018 times)
marat
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Using latent state in circuits
Nov 10th, 2002, 6:57am
 
Hi,
 If I have a circuit with large time constant signals, for example
  counters, and want to use latent state of signals in purpose
  to speed up transient analysis , how can I apply differnet
  time steps?
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rf-design
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Reiner Franke

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Germany
Re: Using latent state in circuits
Reply #1 - Nov 12th, 2002, 8:13am
 
Hi,

you can define in HSIM a voltage change tolerance for a specfic node, or a group of nodes belonging to a subcircuit instance, or all instances of a subcircuit. If the calculated change of node voltage is below your threshold every node dependend on your node is skipped. I have not tried some explicite settings for mintimesteps for specific nodes.

Reiner Franke
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marat
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Re: Using latent state in circuits
Reply #2 - Nov 20th, 2002, 2:31am
 
Thank you for your answer, and for me more interesting underlaying mathematics and physics.
Would you like to describe matrix building for latent
states?
We should marked some blocks in matrix and doesn't evaluate them? Or another algorithms may be possible?
     with best regards, Marat
     
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rf-design
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Reiner Franke

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Re: Using latent state in circuits
Reply #3 - Nov 21st, 2002, 11:02pm
 
Hi Marat,

I do not know how Nassda implement this feature. From my own research interest in the late 80s I know that there is a requirement to trace nodes which depend on this as quiet identified node. In matrix terms it is required to built up a sparse structure matrix, or a graph representing the fills of the nodal matrix. Based on this information you can reorder the update calculation by neglating quiet nodes. Simply only a submatrix is solved. If the circuit formulation is based on hybrid methods there is a more analog method. Based on the structure and a classification of the dynamic matrix you can identify different time steps for state variables or groups of them. I did not know if there is any circuit simulator which could run multirate or use hybrid method.

The involved methods for analysing the circuit structure and modifying the spare matrix method are highly math orientied. I come down to the level of implementing the Dulmage-Mendelsohn decomposition of a structure matrix. That is the base for multirate as well as circuit partioning for parallel processors or strong pipeline engines.

I will open my own page in the next months summarizing my 15 years old knowledge.

Reiner Franke
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