There are a couple of app notes from atmel that specify how the ISP works. Then, it is a matter of implementing that with the prop or any other device. If you use an avr with bootloader (and not the discontinued 90s2313, the replacement is the attiny2313) then you can easily use LVTTL RS-232 interface to program the avr, the simplest method imho.
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Visit some of my articles at Propeller Wiki:
MATH on the propeller propeller.wikispaces.com/MATH
pPropQL: propeller.wikispaces.com/pPropQL
pPropQL020: propeller.wikispaces.com/pPropQL020
OMU for the pPropQL/020 propeller.wikispaces.com/OMU
pPropellerSim - A propeller simulator for ASM development sourceforge.net/projects/ppropellersim
http://forums.parallax.com/forums/default.aspx?f=25&m=240877&g=375123#m375123
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My head is pasming!