Hi Sean,
Please refer to the section 10.24.8 FCM security in the UM11227.
You can download the UM11227 from the NTM88 product page.
BR, Tomas
Dear Sean,
When the NTM88 chips leave our factory, they are only programmed with trim coefficients between 0xFD40 and 0xFDFF. There is no embedded firmware like with the FXTH87. More information is provided in the attached AN12524.
The trim coefficients are necessary to the sensors. When programming an application in the NTM88 chip, the user must make sure that the section between 0xFD40 and 0xFDFF is never erased nor overwritten. The trim page corresponds to the protected range inside the NTM88_LIB.s8p file.
There is a feature inside the FXTH and NTM88 chips that allows the user to secure the chip (more details are provided in the manual). Once the chip is secure it cannot be reprogrammed. The only way to unsecure it permanently is to perform a mass erase. But note that a mass erase will erase the trim coefficients, so the sensors will not be functional anymore.
The security register is located in flash at address 0xFFBF. If this register is equal to 0xFF when a reset is performed, then this will secure the chip. In order to keep the chip unsecure, this register must be written during programming, for example with value 0x82. In the NTM88 starter projects, this byte is set to 0x82 in the main with the instruction highlighted in yellow:
BR, Tomas
