L9908 datasheet(29/153 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 configuration 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 aren`t 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.

Table 19. CFG timeout

Symbol

Parameter

Min

Typ

Max

Unit

Notes

T_cgf_time_out

CFG Mode Time-out

100

Not subject to production test

L9908

Configuration mode

DS13546 - Rev 3

page 29/153

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