JAJSNX3 February 2024 TCAN1465-Q1 , TCAN1469-Q1
ADVANCE INFORMATION
The TCAN1469-Q1 provide advanced bus fault detection. 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 ≥ 2µs. 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 8-34 as an example of node locations and how they can impact the ability to determine the actual fault location. Figure 8-35 through Figure 8-39 show the various bus faults based upon the three node configuration. Table 8-17 shows what can be detected and by which device.
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 |
---|---|---|---|
2 | Open | Open | Depending upon open location the device detects this as no termination. |
3 | Open | Normal | Yes, but cannot tell the difference between Fault 3 and Faults 2 and 4; Device 2 and Device 3 does not see this fault |
4 | Normal | Open | Yes, but cannot tell the difference between Fault 4 and Faults 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 | RSVD | Reserved | |||
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 |