In system field upgrades to an XC9500 CPLD are traditionally done by field engineers using a portable PC. The PC will have either the EZTag or JTAG Programmer Software, an XChecker or JTAG Parallel Cable with flying wires to connect to the target application, and an updated JEDEC programming file. Once all the cables, software, and files are in place, the engineer begins the field upgrade. This application note goes one step further in not requiring the field engineer to be present where the upgrade occurs. It will require advanced planning and building circuitry into the embedded system in advance, but that should be expected.