Partial networking allows a customizable network configuration where only select nodes in a system can respond to a CAN bus wake-up. Traditional CAN bus wake ups only require a wake-up pattern (WUP) to occur before this is recognized as a wake signal. This can be a great way to wake up all devices on the CAN bus through an active CAN device, but not every application needs or wants every CAN device to wake up for every situation. This is where partial networking comes into play – by adding a little more information after the WUP has occurred on the bus each individual CAN device can determine if this needs to wake up or not. There are three main checks that can be performed during partial networking to selectively decide what devices to wake up: ID verification, DLC verification, and data verification.

ID verification is the simplest, and most common, implementation of partial networking. In partial networking each CAN device has an 11-bit ID (classic) or can use an extended 29-bit ID depending on use. Each device within the TCAN28XX line of devices can have the ID altered based on system/application needs. If using partial networking with ID verification (lowest level of partial networking) the IDs that are accepted are a masked version of the devices ID where each bit of the mask represents a care “c” or a don’t care “d” value. If the device ID is 0b11001100110 and the mask string is 0bcccdddddddd that means any ID that meets the following pattern 0b110xxxxxxxx can wake the device up. So that means IDs such as 0b11011111111 and 0b11001010101 are valid IDs that can pass ID verification, but device IDs such as 0b01011111111 and 0b11100000000 can be rejected. This means that when using ID verification only devices that need to talk to each other are active while unneeded nodes are asleep (which saves on power consumption).

Partial networking can include even more layers of verification with DLC and data matching. The DLC field is a 4-bit number that represents how many data bytes to expect where values 0b0000 through 0b1000 represent 0 through 8 bytes respectively that can be used in classical CAN/ CAN FD and all values 0b1001 to 0b1111 represent 8 bytes only for classical CAN. If the DLC is formatted to be 0b0010 then two data bytes are expected and if more or less than that is received the DLC matching has failed. This is only applicable when the data mask bit is set. If the data mask bit is set not only is the DLC matched to make sure proper transmission length, but the data is also matched. The TCAN28XX line of devices can configure 8 bytes of data for data verification. Data verification does work differently than ID verification as is not looking for exact matches as with ID – but just making sure that the incoming data has at least 1 matching 0b1 value. To help clarify this assume a DLC value of 1 (1 byte of data) with configured data within SBC to be 0b01010101 and now imagine two different inputs: 0b00100010 and 0b00000001. The first input 0b00100010 has no matching “1s” when compared to configured data so the first byte can fail data verification, but when looking to the second byte’s bit position 0 this is 1 for both the SBC configured data and the incoming data which means this can pass data verification.

For more details on implementation of partial networking or selective wake please see the specific device data sheet and or firmware guide.