I was hoping the file on Atmel's website with the USB bootloader contained the source code, so it would simply be a matter of reading the code to find out. Alas, the zip file merely contains the .hex file along with some readme files.

A curious thing though: they do have code for the flash API driver, described "This Flash API test package is intended for AT89C51SND1C product with USB bootloader." Does this imply that there is a 'SND1 product WITHOUT the USB bootloader? (i.e., UART bootloader)

I think I'd want to contact my local Atmel FAE to try to get the source for the bootloaders (they are available for the 'CC03) or at least a clarification of ISP procedures.

I suppose they expect you to simply use FLIP without comprehending what it is doing...

Dennis