Answers Database
XC3000/XC3000/XC4000/XC5200: Logic cells and the FPGA Density Cross Reference Guide
Record #1897
Problem Title:
XC3000/XC3000/XC4000/XC5200: Logic cells and the FPGA Density Cross Reference Guide
Problem Description:
Urgency: standard
General Description: What are Logic Cells? How do they relate
to different device architectures including those of different
vendors?
Solution 1:
A "logic cell" (LC) is the primary building block of today's
high density FPGAs and is the best measure of a device's
maximum logic capacity. Logic Cell utilization will vary by
design and product family, thus making the total number of
Logic Cells the best "first pass" capacity comparison metric.
A logic cell consists of a 4-input lookup table and a flip
flop.
If each 4-input LUT and each register are considered 1/2 of a
logic cell, and a 3-input LUT has 3/4 the functionality of a
4 input LUT then each 3 input LUT can be considered 3/8 of a
logic cell. This each xc4000 has 2.375 logic cells.
For more information, as well a comparison of different vendors, and architectures refer to:
http://www.xilinx.com/xbrf/xbrf011.pdf
End of Record #1897 - Last Modified: 01/12/98 11:52 |
