In every single application and use case of these SBCs the SBC mode can need to be configured and in the vast majority, if not all, the CAN transceiver can also need to be configured. For both the TCAN24xx and TCAN28xx line of devices this is done in the same way and primarily only concerns a couple of registers which are SBC_CONFIG (address Ch) and CAN_CNTRL_1 (address 10h). This is not an exhaustive list of SBC configuration registers, but ones that are used in many different applications.

The first register, SBC_CONFIG contains six different configuration options – VCC1_OV_SEL (bit 7), OVCC1_ACTION (bit 6, TCAN24xx only), VEXCC_ILIM_DIS (bit 6, TCAN28xx only), PWM_SEL (bit 5), VCC1_SNK_DIS (bit 4), SBC_MODE_SEL (bits 3-2), VCC2_CFG (bits 1-0). For simplicity assume that bits 7-4 and 1-0 are kept as default conditions – a relatively common use case. Bits 3-2 determine what mode the SBC is in with the following options available: Sleep Mode (0b00), Standby Mode (0b01), and Normal Mode (0b10) – most of the devices active operation can take place in normal mode and the controller must put the device into Normal mode by writing to this register. The controller is the one that can move the SBC into normal mode – the device doesn’t automatically transition so this step must always be done after configuration and during device wake-up.

The second register, CAN_CNTRL_1, concerns the high-level operation of the CAN transceiver and there are 5 different configuration options with one reserved bit: SW_EN (bit 7), TXD_DTO_DIS (bit 6), FD_EN (bit 5), reserved (bit 4), CAN1_FSM_DIS (bit 3), and finally CAN1_TRX_SEL (bit 2-0). For simple configuration only the CAN1_TRX_SEL bitfield is important – there are six different operating modes as well as two reserved bits. The options are: off (0b000), SBC mode Control WUP disabled (0b010), wake capable (0b100 – default condition), listen (0b101), SBC mode control (0b110), on (0b111), with bit patterns 0b001 and 0b011 reserved. The CAN transceiver state is limited by the overall SBC mode with the choice to control the transceiver independently or SBC or have the SBC mode force the CAN transceiver mode (SBC mode control).

To illustrate an example of what to write to the configuration register a quick look at three cases can be shown: Tie SBC mode to CAN mode, turn CAN on independently, turn CAN to listen mode during standby.

CASE 1: Tie SBC mode to CAN mode

Step 1: Power on Device with SW pin held high (assuming SW_POL is default condition)

Step 2: Once device is in standby mode write 0x06 to address 10h; This sets CAN transceiver to SBC Mode Control

Step 3: Write 0x8A (TCAN24xx) | 0x0A (TCAN28xx) to address Ch; this puts the SBC into normal mode, which also forces the CAN transceiver to be in the “On” state.

CASE 2: Control CAN independently of SBC Mode

Step 1: Power on Device with SW pin held high (assuming SW_POL is default condition)

Step 2: Once device is in standby mode write 0x8A (TCAN24xx) | 0x0A (TCAN28xx) to address Ch; this puts the SBC into normal mode – since CAN is not tied to SBC state CAN transceiver stays wake capable.

Step 3: Write 0x07 to address 10h; this can turn on the CAN transceiver – if SBC mode was not in normal this can be an illegal action and cannot be completed.

CASE 3: Set CAN to listen mode during standby.

Step 1: Power on Device with SW pin held high (assuming SW_POL is default condition)

Step 2: Write 0x05 to address 10h; this can set the CAN transceiver to listen mode. Listen is available in standby so no further actions necessary.