In ADuC812BS after 1 year of use Vref (pin8) has changed up to 2.7V and the bootloader also does not work.
How to restore?
Do you have any components connected at Vref? If it suddenly rise that much without anything connected at the vref, I'd say the part has been damaged.
What error are you seeing with the bootloader?
Pin Vref is connected only to the capacitor 0,1uF.
Windows Serial Downloader message:
Operation : Resetting the target device (2)Status : Failed to connect to ADuC8xx after 2 attempts
Your VREF pin connection is correct. If the part was working before, I would say that it got damaged while running the application. We have no way to recover the part if we can't communicate through the boot loader.
My idea - the application makes record on page 160 FLASH/EE of memory data (SECURITY BITS),erased calibration registers ADC.
How to correct?
Calibration registers are not accessible and are written to Flash/EE memory before shipment.
Retrieving data ...