Losing Flash

[philip1]

Posted on February 13, 2008 at 13:17

Losing Flash

[philip1]

Posted on February 07, 2008 at 11:27

We are having problems with STR730 devices wiping part of their Flash memory when they power-up, usually including the lowest addresses which means they wipe their Reset Vector!!

Does anyone know what can cause this? I suspect it may be a problem with the RESET_IN line rising while the power line is also rising but I need some definitive data. Any help much appreciated PhilipJ

[kleshov]

Posted on February 10, 2008 at 14:22

The datasheet says ''An external power-on reset must be provided to ensure the microcontroller starts up correctly''.

You must keep the RSTIN line asserted as long as power supply voltage is below 4.5 volts. This includes power-downs as well as power-ups. I haven't worked with STR73x, but I have seen other microcontrollers erase/overwrite their on-chip flash memory when that requirement is not met.

[sjo]

Posted on February 11, 2008 at 10:13

Are you using a external reset chip, eg. STM811/STM1001?

Cheers sjo

[philip1]

Posted on February 13, 2008 at 13:17

I was but I had to remove it as it kept reseting due to noise on the power line! It was a Max1232 which ''browns out'' at 4.75v and I think noise spikes were setting it off

I am changing it to a different device which has adjustable threshold but I just wanted to see if anyone could absolutely confirm that this is the cause... PhilipJ [ This message was edited by: philipj on 13-02-2008 17:48 ]