This programmer device is specially designed for "serial writable/parallel readable" Flash Storage Devices as the SGS Thomson's PSD micro-controllers and memory flashes. Micro-controllers without internal data code flash memory or less than requirement, need an external flash data memory to store the program data code. Unfortunately, using the external flashes or EEPROMs that they program in parallel, is difficult to reprogram, test and modify the code. The PSD flash memory and uPSD micro-controller devices have a capability to write into it serially (via JTAG connection and PSDsoft Express software) and read from it in parallel while the flash is in the circuit. This circuit enables you to program these flashes in-circuit (ISP Mode) easily. Please note that the schematic which is published by ST has some errors that they have been fixed in this project.