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Browse Prior Art Database

Method to Insure Correct Values Propagated From a Physical Device

IP.com Disclosure Number: IPCOM000034482D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Dubler, JF: AUTHOR [+2]

Abstract

Disclosed is a procedure for guaranteeing that values propagated from a physical device in a logic simulator/physical modeling system are the correct values for that simulation time. Correct values are assured by having the behavioral shell for the physical device wait for the delay time and then propagate the current output values. Using this procedure, no physical device output values are ever propagated into the future. Net values derived from a physical device computation that are scheduled into a future simulation time queue could be incorrect based upon subsequent computations performed prior to the net actually taking on the scheduled value.

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Method to Insure Correct Values Propagated From a Physical Device

Disclosed is a procedure for guaranteeing that values propagated from a physical device in a logic simulator/physical modeling system are the correct values for that simulation time. Correct values are assured by having the behavioral shell for the physical device wait for the delay time and then propagate the current output values. Using this procedure, no physical device output values are ever propagated into the future. Net values derived from a physical device computation that are scheduled into a future simulation time queue could be incorrect based upon subsequent computations performed prior to the net actually taking on the scheduled value. When this condition happens, it is necessary for the simulator to execute the time-consuming instructions necessary to delete the net update event from the future time queue of the simulator. A method is disclosed here which avoids the problem of deleting net update events from future time queues by never scheduling future net update events for physical device output nets. The method consists of providing a buffer to store the output net values from physical devices. Each time a physical device computation occurs, the output net values are stored in this buffer. Rather than schedule these newly computed output values into the future, the method is to have the behavior perform a "wait" for the delay time of the physical device. After the delay time has ex...