L9908TR datasheet(29/152 Pages) STMICROELECTRONICS

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5.4.1

Configuration mode activation

An accidental SRR and SLR change must be avoided therefore a finite state machine is implemented to access

the CONFIG mode.

The CONFIG mode access state machine is composed by 2 sequential states, the passage from a state to the

next one is carried out by the acknowledgment of a dedicated UNLOCK frames sequence to be written in the SPI

The correct completion of the CONFIG mode procedure gives access to SLR. Access to SRR is further masked

until EN_BR = 0 or HBn_DIS = 1 [n = 1, 2, 3].

Table 18. CONFIG mode activation register

CFG_EN_UNLOCK <7:0>

Description

0x55 → 0x33

CONFIG mode access

0xAA

CONFIG mode exit

Note:

•

SRR and SLR configurations will become effective the next clock cycle after the completed writing

operation.

•

Write attempts on SRR and SLR are ignored as long as the previous requirements are not met.

•

Write attempts on Read only (RO) registers are ignored, no matter if the register is NSR, SLR or SRR.

Figure 12. CONFIG mode state machine

The configuration mode is left by a dedicated LOCK frame (LOCK key: 0xAA) to be written in the SPI register

CFG_EN_UNLOCK, which confirms the written changes and locks them on writing. The configuration mode is

also left automatically after the CONFIG mode time-out expiration: if no correct LOCK SPI frame is detected

within T_cgf_time_out, the CONFIG mode is left.

Note:

All parameters are guaranteed and tested in the voltage ranges reported in Table 5 unless otherwise specified.

Where not specified the parametrical operating range equals the functional operating range.

L9908

Functional description

DS13546 - Rev 5

page 29/152

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