As density increases in FPGA families, current serial PROMs cannot handle the programmingpatterns required to configure high-density FPGAs. Larger PROMs have been made availablebut many require addressing schemes that make them unsuitable to interface directly to anFPGA. This application note describes how a small XC9500 CPLD can be used in conjunctionwith a byte-wide PROM to program high-density FPGA devices.