In standby mode, the bus transmitter does not send data nor does the normal mode receiver accept data. There are several blocks that are active in this mode. The low power CAN receiver is actively monitoring the bus for the wake up pattern (WUP). The WAKE pin monitor is active. The SPI interface is active so that the microprocessor can read and write registers in the memory for status and configuration. The INH pin is active in order to supply an enable to the VIO controller if this function is used. The device goes from sleep mode to standby mode automatically upon a bus WUP event, WUF event or a local wake up from the WAKE pin. If VIO is present the device can wake up from a SPI mode change command.
Upon power up, a power on reset or wake event from sleep mode the TCAN114x-Q1 enters standby mode. This starts the SWE timer, tINACTIVE, that requires the processor to either reset the interrupt flags or configure the device to normal or listen modes. This feature makes sure the node will be in the lowest power mode if the processor does not come up properly. This automatic mode change also takes place when the device has been put into sleep mode and receives a wake event, WUP, WUF or LWU. To disable this feature for sleep events register 8'h1C (SWE_DIS) must be set to one. This does not disable the feature when powering up or when a power on reset takes place.
The following provides the description on how selective wake interacts between sleep and standby modes for TCAN1145-Q1 and TCAN1146-Q1.
When in standby mode the RXD pin will be released back to high when the PWRON, LWU, CANINT and FRAME_OVF interrupts have been cleared.