A Simultaneous Technology Mapping, Placement, and Global Routing Algorithm for FPGAs with Path Delay Constraints

Nozomu TOGAWA  Masao SATO  Tatsuo OHTSUKI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E79-A   No.3   pp.321-329
Publication Date: 1996/03/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section of Selected Papers from the 8th Karuizawa Workshop on Circuits and Systems)
FPGA,  technology mapping,  layout,  path delay,  performance optimization,  

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In this paper, we propose a new FPGA design algorithm, Maple-opt, in which technology mapping, placement, and global routing are executed so that the delay of each critical signal path in an input circuit is within a specified upper bound imposed on it. The basic algorithm of Maple-opt is top-down hi-erarchical bi-partitioning of regions. Technology mapping onto logic-blocks of FPGAs, their placement, and global routing are determined simulatenously in each hierarchical process. This simultaneity leads to less congested layout for routing. In addition to that, Maple-opt computes a lower bound of delay for each path with a constraint value and determines critical paths based on the difference between the lower bound and the constraint value dynamically in each hierarchical process. Two delay reduction processes are executed for the critical paths; one is routing delay reduction and the other is logic-block delay reduction. Routing delay reduction is realized such that, when bi-partitioning a region, each constrained path is assigned to one subregion. Logic-block delay reduction is realized such that each constrained path is mapped onto fewer logic-blocks. Experimental results for some benchmark circuits show its efficiency and effectiveness.