L9788 datasheet(152/264 Pages) STMICROELECTRONICS

152 / 264 page

CAN FD interface

L9788

152/264

DS12308 Rev 4

12.8.3

No pattern wake up

If the CAN pattern wake up option is disabled (CAN_PATTERN_EN = '0') and the wake up

enable bit is set (CAN_WAKEUP_EN = '1') and the transceiver is in Low-power mode, a

dominant state on CAN BUS for more than tfilter will cause a Wake-up detection.

Figure 68. CAN wake up options

12.9

Automatic voltage biasing

If the CAN transceiver is in Low-power mode (CAN_EN = 0 or U-CHIP OFF) and the

automatic voltage biasing is active (CAN_AUTO_BIAS = '1', MSC_CONFIG-REG21[7) if

there has been no activity on the bus for longer than tSILENCE, the bus lines are biased

towards 0 V via the receiver input resistors RCANH/RCANL (biasing disabled) and the MSC

flag CAN_SILENT is set to 1. If the wake up option is enabled (CAN_WAKEUP_EN = '1')

and a wake-up activity on the bus lines is detected (wake-up pattern or no pattern), the bus

lines are biased to VCANHrec respectively VCANLrec via the internal receiver input

resistors RCANH/RCANL also the MSC bit WAKE_UP_CAN_DET_AUTO is latched (MSC

UPSTREAM READ 12, Frame3). The biasing is activated not later than tBias.

12.10

CAN reset matrix

In the reset matrix table there is a row dedicated to CAN.

Reset matrix *12 source means that at least one of the following faults is active:



VDD5_OV;



OSC FAULT;



TNL;



RST_N.

GADG0912161440PS

Normal Pattern wake-up

No Pattern wake-up

CANH-CANL

U-CHIP STATE

CANH-CANL

U-CHIP STATE

OFF

>tfilter

>twake

tfilter

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