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# Interactive Timing Analysis

IP.com Disclosure Number: IPCOM000051482D
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 1 page(s) / 12K

IBM

## Related People

Donath, WE: AUTHOR

## Abstract

In the timing analysis of a system, it is often necessary to evaluate the path delays involved in the system when changes occur to an already characterized system. Currently, this requires that a calculation be performed for every block in a graph, where the "blocks" correspond to various portions of the system. To reduce the test time, it is proposed to test only the activated or changed conditions such that calculations are performed only on those blocks which actually change, rather than performing calculations on the entire system.

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Interactive Timing Analysis

In the timing analysis of a system, it is often necessary to evaluate the path delays involved in the system when changes occur to an already characterized system. Currently, this requires that a calculation be performed for every block in a graph, where the "blocks" correspond to various portions of the system. To reduce the test time, it is proposed to test only the activated or changed conditions such that calculations are performed only on those blocks which actually change, rather than performing calculations on the entire system.

In timing analysis, delays are propagated through the system organized in "blocks" which are "levelized". In general, primary inputs and latches are at level
0. Any block, whose inputs are only at level 0, is at level 1. This relationship is recursively used to determine that a block may be at level e if none of its input blocks has a level exceeding (e-1) and at least one input block has a level value of (e-1).

Consider a levelized graph. For each block there is a level value as well as space for a pointer to another block, where normally this space is empty. Furthermore, there is a vector of level-source pointer, whose entries range from 0 to index max (e), i.e., the maximum of all level values in the graph.

The standard timing analysis calculation takes all the blocks on each level (initially level 0) and calculates for each block, from the arrival time of the input blocks, the arrival time of that pa...