The details are there (pg. 177 of the users manual. I seem to remember they wern't all there in the previous rev of the users manual). There is also a windows utility available that downloads over the serial port which is what I'm using now. I haven't tried to write one myself but it looks fairly straightforward, all the timing is taken care of on chip. Hardware wise you just need power, Rx, Tx and pull one additional pin down on reset to trigger boot load mode.
Robert Adsett