L99DZ320 datasheet(60/146 Pages) STMICROELECTRONICS

60 / 146 page

The CAN receiver is not disabled in case of any failure condition.

Dominant TXDC time out

If TXDC is in dominant state (low) for t > tdom(TXDC) the transmitter is disabled, status bit is latched and can be

read and optionally cleared by SPI. The transmitter remains disabled until the status register is cleared.

CAN Bus permanent recessive

If TXDC changes to dominant (low) state but CAN bus does not follow for 4 times, the transmitter is disabled,

status bit is latched and can be read and optionally cleared by SPI. The transmitter remains disabled until the

status register is cleared.

CAN permanent dominant

If the bus state is dominant (low) for t > tCAN a permanent dominant status is detected. The status is latched and

can be read and optionally cleared by SPI. The transmitter is not disabled.

RXDC permanent recessive

If RXDC pin is clamped to recessive (high) state, the controller is not able to recognize a bus dominant state and

could start messages at any time, which results in disturbing the overall bus communication. Therefore, if RXDC

does not follow TXDC for 4 times the transmitter is disabled. The status bit is latched and can be read and

optionally cleared by SPI. The transmitter remains disabled until the status register is cleared.

3.10.4

Wake up by CAN

The default setting for the wake-up behavior after Power-on Reset is the wake-up by regular communication on

the CAN bus. When the CAN transceiver is in a standby mode (CAN TRX STBY) the device can be woken up by

sending 2 consecutive dominant bits separated by a recessive bit.

Normal pattern wake-up can occur when the CAN pattern wake-up option is enabled, and the CAN transceiver

was set in standby mode (CAN TRX STBY) while CAN bus was in recessive (high) state or dominant (low) state.

In order to wake-up the device, the following criteria must be fulfilled:

•

The CAN interface wake-up receiver must receive a series of two consecutive valid dominant pulses, each

of which must be longer than tfilter.

•

The distance between 2 pulses must be longer than tfilter.

•

The two pulses must occur within a time frame of twake.

•

Wake-up occurs when duration of the second pulse becomes longer than tfilter.

Note:

A wake-up caused by a message on the bus starts the voltage regulator and the microcontroller to switch the

application back to normal operation mode.

L99DZ320

Functional description

DS14235 - Rev 5

page 60/146

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