L9788 datasheet(34/264 Pages) STMICROELECTRONICS

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Operation behavior

L9788

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DS12308 Rev 4

Count up

Wake up Timer shall count up the timer from 1 while the MSC Wake Up Timer Start command

is given. When Wake Up Timer Stop command is given, the Wake Up Timer shall stop

counting and hold the value until Wake Up Timer Start command is given again. While the

counter is counting the EOT_STATUS will be 1. If it's not counting EOT_STATUS will be 0.

Wake Up Timer start/stop commands

Wake Up Timer counts up when msc start command in the MSC

WAKE_UP_TIMER_START_STOP register is given. When the msc stop command in the

MSC WAKE_UP_TIMER_START_STOP register is given the timer shall stop counting up

but hold the WAKE_UP_TIMER_CNT Register. The bit can be set or reset via MSC.

WAKE_UP_TIMER_CNT Register

WAKE_UP_TIMER_CNT Register consists of 24 bits it's Read Only. The range of

WAKE_UP_TIMER_CNT is from 0 (h'000000) to 16777215 (h'FFFFFF).

WAKE_UP_TIMER_CNT Register is set to 0 (h'00000) when power on reset of VB_STBY

occurs. WAKE_UP_TIMER_CNT Register is set to all "0" via MSC when power on reset

period or VB_STBY is open.

Wake up timer_SET time register

The Wake up timer_SET register consists of 24 bits. And the register is Read and Write register.

The range of Wake up timer_SET is from 0 (h'000000) to 16777215 (h'FFFFFF). Wake Up

Timer_SET Register is set to 0(h '000000) when power on reset of VB_STBY occurs.

EOT function 1

EOT Function 1 - count “stand” time: After the start of the counter, the counter starts to count

up till the value that has to be set before starting it using Wake_up_timer_SET. If ECU

switches on before the counter reaches the wake up timer_set value, the µC can read the

“stand” time via MSC. If the counter reaches the wake up timer_set value before ECU

switches on, the count keeps the wake up timer_set value.

This function is selected with MSC CONFIG_REG6[6]=EOT_MODE=0. The EOT function 1

does not set WAKE_UP_EOT_DET at 1. EOT_MODE bit can be correctly read only when

wake up timer logic is working, else it is read 0.

VB_STBY must be provided to correctly read the EOT_MODE bit. If VB_STBY is removed

the register content will be lost.

EOT function 2

EOT Function 2 - wake-up via WAKE_UP_TIMER_SET. Set WAKE_UP_TIMER_SET

(CONFIG-REG15-0 / CONFIG-REG15-1/ CONFIG-REG15-2) to a certain value, then start

the counter before shutting down the ECU. The counter counts up until the

WAKE_UP_TIMER_SET is reached. The reaching of WAKE_UP_TIMER_SET activates the

wake signal and will start a wake-up sequence. This function is selected with MSC

CONFIG_REG6[6]=EOT_MODE=1. EOT_MODE bit can be correctly read only when

wake-up timer logic is working, else it is read 0.

VB_STBY supply must be provided to correctly read the EOT_MODE bit.

L9788 Datasheet(PDF) 34 Page - STMicroelectronics

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