Flimsy Flash CY8C21434 | Cypress Semiconductor
Flimsy Flash CY8C21434
Dear Sirs, I'm trying to solve a problem on a capacitive keyboard that is quite odd.
Sometimes the capacitive keyboard is stuck and doesn't works no more; just a re-programmation of the mcu CY8C21434 solves the block of the capacitive keyboard. We obtain the block just doing some voltage dips on the main supply.
On different boards after 230V interruption the flash of the microcontroller is completely zeroed (every single byte is 0x00) and in some rare cases the flash mem is just corrupted (checksum different from hex).
No writing to flash are done in the firmware.
In the first firmware there was no watchdog and no LVD enabled moreover there was the CPU_Clock setted to work @ SYSCLK/1 but the supply voltage was 3.3V and this is not allowed (datasheet page 19/50) because the oscillator operates outside the valid operation region (yes the cpu in most cases works also outside VOR).
With a new FW with WDG, LVD enabled and SYSCLK/4 (so now working inside the VOR) all seems to work correctly and there are no blocks.
Now If i can accept a flash corruption (there is acompressor near the board) I can't explain ho can all the flash to be erased.
Can someone tell me how the mcu can be completely erased
Best regards and many thanx to anyone will help