Introduction to FPGA’s

1. Introduction to FPGA’s • FPGA (Field Programmable Gate Array) • ASIC chips provide the highest performance, but can only perform the function they were designed for. • FPGA’s can be reprogrammed using HDL’s or other design methods to implement a incredible variety of functions • Allow for efficient and cost-effective prototyping • Cost of FPGA chips is very low compared to ASIC’s because they are not specialized for a specific task

2. FPGA: Configurable Logic Blocks • Essential FPGA component • Each CLB can be reprogrammed to implement a basic sequential or combinational circuit • Create array of CLB’s • At intersection of wires are switches • Form switching matrix

3. FPGA: Configurable Logic Blocks • Two 16x1 RAM blocks • 8x1 RAM block • 2 Edge-triggered D flip-flops • Multiplexers used to configure interconnects • Newer FPGA’s provide other additional hardware features

4. FPGA: Configurable Logic Blocks • RAM blocks act as Look Up Tables • Used to implement combinational functions • By using all 3 LUT’s, can implement any Boolean function of 5 variables

5. FPGA: Switching Network • PSM: programmable switching matrix configured to connect vertical and horizontal wires • Singles: connect adjacent PSMs • Doubles: connect every other PSM (traverses 2 CLBs) • Quad: traverses 4 CLBs • Global: run entire length of chip. Use tristate buffers and can be used as buses shared by several CLBs • Purpose: allows signals to be routed through fewer switching points • Global nets: low-skew signal network for high fan-out signals (clocks and reset signals)

6. FPGA Design Flow

7. XILINX FPGA comparison Source: www.xilinx.com

8. Reference(s) • Introductory VHDL From Simulation to Synthesis, Sudhakar Yalamanchili, Prentice-Hall, Inc., 2001.