RAM values

[vikram]

Posted on May 10, 2006 at 07:51

RAM values

[vikram]

Posted on May 10, 2006 at 06:16

Hello Everyone,

I have a question regarding the RAM Area of the ST72F521R9T microcontroller. its RAM range is from 0x200 to 0x87F.

Inorder to distinguish from the bootloader and the application i have preserved a location in the RAM which will not be initialised to 0 at the startup ,so that based on that location the bootloader can decide to go to appln or soft upload mode.

i used values 0x00 for application and 0xFF for download mode, but now on some boards i saw that the application was not starting ,upon debugging i found that in that board as soon as the power was switched off and powered on the location which i had used to distinguish between application mode and upload mode becomes by default 0xFF every time i put off the power and put it on again,

can you help me to solve this problem

also on my board i dont have any I2C EEPROM so that i could had used that for storing the variable.

waiting for the reply,

Thanks

Vikram S.M.

[sjo]

Posted on May 10, 2006 at 07:51

At a cold reset the ram value is undefined, so your approach will not work.

Why not use a crc checksum which you write after programming the appli flash.

If the checksum is ok run appli if not run your bootloader. This is the common method used.

Regards

sjo