Re: [avrdude-dev] programming 128

[Theodore A. Roth]

On Thu, 15 May 2003, Erick   Castillo wrote:

:) The bits read all zeroes because of some strange electrical problem I'm
:) having. For some reason, when I start the board up at 5 volts, the
:) controller doesn't respond nicely... in fact, it does nothing. If I step
:) up the voltage, I notice that the controller responds to 3 volts and runs
:) the loaded program just fine. I've got the atmega128 which is rated to
:) operate between 4.5-5.5V so it should work fine with 5V at boot up. Any
:) ideas why the controller only works when initiated with 3.5-3.7V?

When Atmel (other manufacturers too probably) makes a certain device,
say mega128, they have various speed grades and voltage grades. All
come off the same wafer. The only difference between a 5v part and at
3.3v (LV) is how the set the secret internal mode fuses of the device
(and whether it passes tests in that mode). The mode fuses are
accuessible to anyone if you know the secret hand-shake. Usually done
with either a special SPI command or a special hi-v programming
operation (take lines x, y, z to 12V, send these commands, etc).

It's possible (although not very likely) that you have a device that
has some bogus fuse mode.

Has the device ever worked?

Ted Roth