L9965P datasheet(83/104 Pages) STMICROELECTRONICS

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3.18.1

NVM read/write operations

NVM data is automatically downloaded into local registers every time that the IC FSM transitions from the OFF

state to the DEEP-SLEEP state.

When the IC performs FSM transitions to DEEP-SLEEP state, a selected group of data stored in local registers is

retained to guarantee IC correct operation (managed by nPOR_SLEEP), while all other data is lost (managed by

nPOR_MAIN). Such data will be redownloaded in the next transition to NORMAL or DIAG state.

When the IC performs FSM transitions to OFF state, all data stored in local registers is lost; NVM data will be

redownloaded in the next transition to NORMAL or DIAG state.

In NORMAL state, the following commands in NVM_OP_CMD register allow user interaction with the NVM:

•

NVM_OPERATION = 0x3 triggers the NVM upload and refresh: this operation fetches the data previously

written into configuration registers and writes it to the relative NVM sectors, then it automatically triggers a

full NVM redownload to guarantee whole data consistency. The operation lasts tNVM_UPLOAD and during

such time interval the MCU will not be able to perform R/W operations (any command will be discarded).

•

NVM_OPERATION = 0x5 triggers the NVM refresh, fetching the data from NVM sectors and writing it to the

configuration registers. The operation lasts tNVM_DOWNLOAD and during such time interval the MCU will not

be able to perform R/W operations (any command will be discarded).

During NVM upload/download operations, the NVM_BUSY flag indicates that NVM is busy. During such an

interval, it is highly recommended to avoid triggering conversions or actuating loads, as the trimming and

calibration data is being refreshed, and data through SPI are not available (read commands return all zeros).

Once the task is complete, the NVM_BUSY bit is set low and the NVM circuit is kept under reset.

In NVM upload operations, NVM_ERASE_VERIFY_ERROR flag indicates that an error has occurred during NVM

erasing, NVM_PROGRAM_VERIFY_ERROR flag indicates that an error has occurred during NVM programming.

Note:

Before interacting with the NVM, the MCU shall hold CWUP high to prevent the IC moving back to DEEP-

SLEEP due to communication timeout.

Every time a write operation is performed, the IC automatically decrements by one the NVM write counter that

starts from 31. The counter value is stored in the NVM as well and is user-accessible reading

NVM_UPLOAD_COUNT bit (read-only). As the number of write operations reaches NNVM_WRITE_CYCLES limit, the

counter has reached the zero value and it will be never be updated anymore. When such a limit is exceeded, data

retention is not guaranteed anymore. By the way, the IC continues to accept and perform every write operation,

even if it is beyond NNVM_WRITE_CYCLES count.

L9965P

Functional description

DS14702 - Rev 4

page 83/104

L9965P Datasheet(PDF) 83 Page - STMicroelectronics