L99DZ320 datasheet(49/146 Pages) STMICROELECTRONICS

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3.4

Wake-up from standby modes

A wake-up from standby mode switches the device to active mode. This can be initiated by one or more of the

following events:

Table 50. Wake-up sources

Wake-up source

Description

LIN bus activity

Can be disabled by SPI

CAN bus activity

Can be disabled by SPI

Level change of EI

Can be configured or disabled by SPI

IV1 > Icmp

Device remains in V1_Standby mode but watchdog is enabled (if ICMP = 0).

No interrupt is generated.

Timer interrupt /

Wake-up of microcontroller by

TIMER

Programmable by SPI:

- V1_Standby mode:

device wakes up and interrupt signal is generated at RXDL/NINT when programmable

time-out has elapsed

- VBAT_Standby mode: device wakes up after programmable timer expiration. V1

regulator is turned on and NReset signal is generated when programmable time-out has

elapsed

SPI access

Always active (except in VBAT_Standby mode)

Wake-up event: CSN falling edge

To prevent the system from a deadlock condition (no wake-up from standby possible) a configuration where the

wake-up by LIN and HS CAN are both disabled, is not allowed. All wake-up sources are configured to default

values in case of such invalid setting. The SPI error bit (SPIE) in the global status register is set.

3.4.1

External interrupts

The EI1 and EI2 inputs can be configured as wake-up sources. Each external interrupt input is sensitive to any

level transition (positive and negative edge) and can be configured for static or cyclic monitoring of the input

voltage level by the suitable setting of the CR18 [8, 9, 14 and 15] bits (EIx_FILT_0 and EIx_FILT_1, with x = 1, 2)

which allows to choose the monitoring among static, cyclic with timer1 or cyclic with timer2. When the

configuration of a timer is changed, the timer is automatically restarted using the new configuration.

For static contact monitoring, a filter time of twu_stat is implemented. The filter is started when the input voltage

passes the specified threshold Vwu_th. External interrupt status bit is set only if this threshold is passed for more

than twu_stat (SR4 bit 21 for EI2_STATE, SR4 bit 18 for EI1_STATE).

Cyclic contact monitoring allows instead the periodical (not threshold dependent) activation of the external

interrupt input to read the status of the external contact. The periodical activations are driven by timer1 or timer2

whose settings (on time and period) can be configured through CR17 (8...13) and (16...21) bits. The input signal

is filtered with a filter time of tWU_cyc after a delay (80% of the configured timer on time). An external interrupt is

processed if the status has changed versus the previous cycle, therefore the external interrupt status bit (SR4) is

set only if the status during the consecutive on time is different, after configuring the delay and tWU_cyc.

The buffered output HS0 can be used to supply the external contacts with the timer setting according to the cyclic

monitoring of the external interrupt input.

L99DZ320

Functional description

DS14235 - Rev 5

page 49/146

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