L9912 datasheet(60/84 Pages) STMICROELECTRONICS

60 / 84 page

SPI interface

L9912

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DocID029639 Rev 2

Figure 25. SPI timing diagram

13.4

SPI registers

L9912 registers, accessed through SPI interface, can be distinguished in



READ ONLY REGISTER/BITS (RO): these registers/bits are used to give system

status and configuration information.

Status bits in read register contain the latched status of the relevant information.



READ AND CLEAR REGISTER/BITS (RC): these registers/bits are used to give

system status and configuration information.

Status bits in read register contain the latched status of the relevant information.

These bits are automatically cleared by a read operation if the data field of the SPI

word transmitted by the microcontroller to the Smart Power is 0x0A5.



READ/WRITE REGISTERS (RW): these register are used to set system configuration

and parameters and to activate/deactivate system outputs.

A write operation returns the previous register value.



WRITE ONLY REGISTERS (WO)/BITS, when read back don't return the previously

written value.

In some read/write registers there are read only bits.

Some registers are locked and a write access must be preceded by an unlock operation.

Table 41. SPI register

R/W

Description

SYSTEM / UNLOCK [13.4.10]

R/W

0x01

This register can be used to unlock some protected

system configurations

SYSTEM OPERATION [13.4.11]

R/W

0x02

This LOCKED register is used to configure the system

behavior

EXTERNAL POWER MOS [13.4.12]

R/W

0x03

This register is used to configure the parameter of the

external power MOS driver

WAKE-UP SOURCES AND DFM GEN

SETUP [13.4.13]

R/W

0x04

This register is used to enable or disable the wake-up

sources and configure the parameter of the DFM

signal (frequency and polarity)

DFMONITOR PWM D.C. [13.4.14]

R/W

0x05

This register is used to configure the parameter of the

DFM signal duty cycle

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