First Advisor

Rolf Schaumann

Term of Graduation

Fall 1997

Date of Publication


Document Type


Degree Name

Master of Science (M.S.) in Electrical and Computer Engineering


Electrical and Computer Engineering




Routers (Computer networks), Field programmable gate arrays



Physical Description

1 online resource (vii, 104 pages)


Based on the concept of Cell Binary Tree (CBT), a new technique for mapping combination circuits into ATMEL 6000 Architecture FPGAs is presented in this thesis. Cell Binary Tree (CBT) is a net-list representation of combinational circuits. For each node of CBT there is a distinguished variable associated with it, the node itself represents a certain logic function, which is selected according to target FPGA architecture. The proposed CBT placement algorithms preserve local connectivity and allow better mapping into ATMEL FPGA. Experiments reveal that the new mapping technique achieved reduction in a number buses used for routing comparing with previously proposed Modified Squashed Binary Tree (MSBT) approach and possibly reduction of area as well. In general, the new technique is realized through following four major steps:

1. Grouping and generating CBT: This is a step to read blifformat file, which is the result of logic synthesis, into a CBT data structure through grouping algorithm, which is a process of gathering logic functions into nodes for mapping based on a targeted FPGA architecture. The main objective of creating CBT is to generate a minimum number of nodes (or cells) to be mapped.

2. CBT placement: Upon getting the minimum number of nodes in CBT to be mapped, the next step is to map those nodes into cells in FPGA. The significance of the placement method in this thesis is to lineup the cells with the same variable into the same row in the FPGA.

3. Bus Assignment: The process of assigning variables to local buses, which run in two possible directions; horizontal and vertical. ATMEL 6000 has two horizontal buses and two vertical buses for each cell. The assignment is based on the number of times a variable appears in a row or column.

4. Routing: The last stage of the process is the connecting cells which have the same input variable. One of the important steps in the routing process is to choose connection bridge cells with the minimum impact on the area.


© 1997 Songhua Zhang

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