The HPR3V3 is an optional accessory to the PRESTO programmer for programming of stand-alone 3.3V devices (as for example DataFlash Memories). The PRESTO programmer can supply a programmed device with 5V. However, some devices require 3.3V supply voltage and 3.3V logic levels on their pins. In such case, the HPR3V3 level shifter or an external 3.3V power supply has to be used.