ZHCSPG0 December 2021 TCAN1167-Q1
PRODUCTION DATA
The TCAN1167-Q1 provides advanced bus fault detection. TCAN1167-Q1 is used for illustration purposes. The device can determine certain fault conditions and set a status/interrupt flag so that the MCU can understand what the fault is. Detection takes place and is recorded if the fault is present during four dominant to recessive transitions with each dominant bit being ≥ 2 μs. As with any bus architecture where termination resistors are at each end not every fault can be specified to the lowest level, meaning exact location. The fault detection circuitry is monitoring the CANH and CANL pins (currents) to determine if there is a short to battery, short to ground, short to each other or opens. From a system perspective, the location of the device can impact what fault can be detected. See Figure 9-8 as an example of node locations and how they can impact the ability to determine the actual fault location. Figure 9-9 through Figure 9-13 show the various bus faults based upon the three node configuration. Table 9-10 shows what can be detected and by which device. Fault 1 is detected as ? termination and Fault 2 is detected as no termination.
Bus fault detection is a system-level situation. If the fault is occurring at the ECU then the general communication of the bus is compromised. For complete coverage of a node a system level diagnostic step for each node and the ability to communicate this back to a central point is needed.
| Fault # | CANH | CANL | Fault Detected |
|---|---|---|---|
| 1 | Open | Open | All positions see this fault as half termination and detect them |
| 2 | Open | Open | Depending upon open location the device detects this as no termination. |
| 3 | Open | Normal | Yes but cannot tell the difference between it and Fault 2 and 4; Device 2 and Device 3 does not see this fault |
| 4 | Normal | Open | Yes but cannot tell the difference between it and Fault 2 and 3; Device 2 and Device 3 does not see this fault |
| 5 | Shorted to CANL | Shorted to CANH | Yes but not location |
| 6 | Shorted to Vbat | Normal | Yes but not location |
| 7 | Shorted to GND | Normal | Yes but cannot tell the difference between this and Fault 10 |
| 8 | Normal | Shorted to Vbat | Yes but cannot tell the difference between this and Fault 11 |
| 9 | Normal | Shorted to GND | Yes but not location |
| 10 | Shorted to GND | Shorted to GND | Yes but cannot tell the difference between this and Fault 7 |
| 11 | Shorted to Vbat | Shorted to Vbat | Yes but cannot tell the difference between this and Fault 8 |
| Address | BIT(S) | DEFAULT | FLAG | DESCRIPTION | FAULT DETECTED | ACCESS |
|---|---|---|---|---|---|---|
| 8'h54 | 7 | 1'b0 | RSVD | Reserved | ||
| 6 | 1'b0 | CANBUSTERMOPEN | CAN Bus has one termination point open | Fault 1 | R/WC | |
| 5 | 1'b0 | CANHCANL | CANH and CANL Shorted Together | Fault 5 | R/WC | |
| 4 | 1'b0 | CANHBAT | CANH Shorted to Vbat | Fault 6 | R/WC | |
| 3 | 1'b0 | CANLGND | CANL Shorted to GND | Fault 9 | R/WC | |
| 2 | 1'b0 | CANBUSOPEN | CAN Bus Open (One of three possible places) | Faults 2, 3 and 4 | R/WC | |
| 1 | 1'b0 | CANBUSGND | CANH Shorted to GND or Both CANH & CANL Shorted to GND | Faults 7 and 10 | R/WC | |
| 0 | 1'b0 | CANBUSBAT | CANL Shorted to Vbat or Both CANH & CANL Shorted to Vbat | Faults 8 and 11 | R/WC |