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Modeling Line Card Loading on a Bus

IP.com Disclosure Number: IPCOM000035029D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Downey, JH: AUTHOR

Abstract

A technique is described which allows the circuit analysis program (ASTAP) to insert and remove line card models from the TDM Shelf Bus during a Monte Carlo analysis. This results in an automatic and random loading on the bus. The bus contains 24 slots. Any type of line card can be inserted into any one of the slots. Each type of line card has an unique interface impedance. A problem arises when trying to model the random loading on the bus. Assume the interface impedance of N-1 line cards have been modeled. There are N total models when an empty slot modeled as infinite impedance is included. The N unique models are connected to each slot via N resistors, as shown in the figure. Zi represents the impedance of the ith model. The resistor Ri connects the ith model to the slot.

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Modeling Line Card Loading on a Bus

A technique is described which allows the circuit analysis program (ASTAP) to insert and remove line card models from the TDM Shelf Bus during a Monte Carlo analysis. This results in an automatic and random loading on the bus. The bus contains 24 slots. Any type of line card can be inserted into any one of the slots. Each type of line card has an unique interface impedance. A problem arises when trying to model the random loading on the bus. Assume the interface impedance of N-1 line cards have been modeled. There are N total models when an empty slot modeled as infinite impedance is included. The N unique models are connected to each slot via N resistors, as shown in the figure. Zi represents the impedance of the ith model. The resistor Ri connects the ith model to the slot. The ith resistor value is calculated from the equation: Ri = K x ABS (i - D), where K = a very large (infinite) resistance, and D = a point distribution with N discrete values ranging from 1 to N. ABS = absolute value There are 24 separate point distributions in the bus model (one distribution for each slot). When a Monte Carlo analysis is performed, a random point is picked from the distribution. The point forces the value of the ith resistor to 0 and thereby enabling the ith line card. All other cards are isolated from the bus by some multiple of "infinite" resistance. The same method is applied to the other 23 slots. This results in the automatic and ra...