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Electronics => Electronics => Topic started by: tristantech on March 11, 2009, 07:54:33 PM

Title: Are AVR fuses resetable???
Post by: tristantech on March 11, 2009, 07:54:33 PM
Can AVR Fuses be reset and reprogrammed? I know that RSTDISBL will brick the microcontroller, but what about the other fuses like CLKDIV8, EESAVE, etc???
Title: Re: Are AVR fuses resetable???
Post by: Webbot on March 11, 2009, 11:10:30 PM
CLKDIV8 - can certainly be reset as can 'most' of them.

Obviously you've found the 'reset disable' problem. Programmers like AVRISP mkII (and probably all of them?) connect with the reset pin. So disabling the reset will effectively mean 'disable talking to me anymore'.

You may wonder why such a fuse exists? Well its probably to stop a competitor taking your chip and reading the program out of it. So the chip becomes a read-only brick. Which for a developer is bad!


Title: Re: Are AVR fuses resetable???
Post by: pomprocker on March 12, 2009, 10:03:45 AM
Yes in the data sheet in all atmegas there is a section on high voltage programming algorithms. With this you can program, high low and extended fuses. HV programming does not depend on reset pin or isp pins
Title: Re: Are AVR fuses resetable???
Post by: want2learn on March 14, 2009, 01:41:08 PM
Just incase you missed this:

http://www.societyofrobots.com/member_tutorials/node/239 (http://www.societyofrobots.com/member_tutorials/node/239)