Single Wire CAN

Single wire CAN is found primarily in specialty automotive applications and emphasizes low cost. Defined in the SAE 2411 specification, single wire CAN uses only one single-ended CAN data wire, as opposed to the differential CAN wires found in most applications. The reduced noise immunity of single wire CAN limit its speed compared to the other CAN physical layers.

Single wire CAN offers four communication modes. The first two modes relate the CAN bus speed. The first mode, Normal Mode, allows the controller to run at 33.333 Kbits/s and is the mode the bus runs in when conducting in-vehicle traffic. The second mode, High Speed Mode, allows the controller to run at 83.333 Kbits/s and is for data download when attached to an offboard tester ECU.

When running in either of the first two modes, the nominal voltage levels are 0 V and 4 V. If a controller goes into Sleep Mode, it ignores all traffic running at these voltage levels. The final mode is called High Voltage Wakeup mode and transmits only at normal communication speeds at nominal voltage levels of 0 V and 12 V (actual high voltage is typically close to V_bat). If a controller goes into Sleep Mode, it wakes up when receiving a CAN frame at the high-voltage signaling levels.