SPSB081 datasheet(31/135 Pages) STMICROELECTRONICS

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3.12.3

CAN transceiver operating modes

Figure 20. Transceiver state diagram

TRX normal mode

Full functionality of the CAN-FD transceiver is available (transmitter and receiver) and the automatic voltage

biasing is enabled.

State transitions from TRX normal mode to VBAT_Standby mode and V1_Standby mode are possible. No

interrupt is generated in this mode.

CAN TRX STBY mode

The CAN-Transmitter is disabled in this mode and the RxD_C pin is kept at high (recessive) level. CAN-Receiver

is capable of detecting a wake-up pattern (WUP). In V1_standby mode and VBAT_Standby mode, a WUP is

indicated to the microcontroller by an interrupt signal.

There is no automatic state transition into TRX normal mode in case of a detected CAN wake up signal (WUP).

In active mode, the microcontroller can initiate a state transition into TRX normal mode by setting the SPI bit

CAN_ACT to '1' and can start communication after TBias.

Moreover, in this mode two further submodes are possible (“Bias ON” or “Bias OFF”), depending on

CAN_AUTO_BIAS bit (compliant with ISO 11898-2:2016) or timeout conditions. In any case, when entering CAN

TRX STBY mode, transition is always to the state “Bias ON”.

3.12.4

CAN error handling

The devices provide the following four error handling features.

After power-on reset (VSREG > VPOR), the CAN transceiver is disabled. The transceiver is enabled by setting

CAN_ACT = 1.

The CAN transmitter is disabled automatically in case of the following errors:

SPSB081

CAN FD bus transceiver

DS14048 - Rev 1

page 31/135

SPSB081 Datasheet(PDF) 31 Page - STMicroelectronics