Verifying the Complete CAN Standby Wake Request Path

A CAN transceiver can recognize bus activity in standby while the controller remains asleep. Recognition is only the first step in waking the node. The request must reach a powered input, cause the intended processor response, and lead to a controlled return to normal communication. Test that complete sequence.

Identify standby receiver behavior

The TI TCAN1042H family data sheet describes filtered wake-pattern recognition and indication through RXD in standby. This low-power behavior differs from ordinary reception of every bus bit in normal mode.

Record the exact device variant, standby control state, supply arrangement, and processor wake-input configuration. Confirm which circuits remain powered while the product sleeps.

Capture the request path

Observe the bus, transceiver RXD, standby control, and a reliable indication that the processor has resumed. Trigger on a controlled wake attempt and preserve enough history to see the node’s previous sleep state.

Check that the electrical level on RXD is compatible with the receiving domain during sleep. A valid transceiver output cannot wake an input whose supply or wake capability is disabled.

Separate qualification from communication

Use the documented wake pattern and filter conditions rather than assuming that any short dominant pulse must wake the device. Compare accepted and rejected stimuli within the supported test conditions.

After recognition, measure the time required to leave standby and become ready for ordinary frames. The frame that caused wake activity should not automatically be assumed available as a normal received message.

Exercise realistic sleep transitions

Test a wake attempt just before, during, and after the software sleep sequence. Check whether interrupt clearing, pin reconfiguration, or power-domain changes create a window in which a request is lost.

For example, clearing a pending wake indication after the processor has already decided to sleep can discard an event that arrived during that decision. Correlate firmware markers with electrical captures to locate such timing windows.

Repeat with a quiet bus and with representative surrounding traffic. Record unintended wakeups as well as missed requests. A configuration that wakes reliably but never remains asleep may still fail the product’s power requirement.

Verify the return to communication, including transceiver mode control and the controller’s expected bus state. Measure the final sleep current only after the node has reached the intended stable state.

Save the wake-state diagram, accepted stimulus, timing captures, and repeated transition results. The completed evidence should show that the complete node wakes and resumes as intended, with the transceiver’s request behavior distinguished from the processor and application actions that follow it.