TJA1043

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Product data sheet

Rev. 3 — 24 April 2013

9 of 27

NXP Semiconductors

TJA1043

High-speed CAN transceiver

be set in Standby mode, Go-to-Sleep mode or Sleep mode. Setting the Wake flag clears

7.2.5 Wake-up source flag

Wake-up source recognition is provided via the Wake-up source flag, which is set when

the Wake flag is set by a local wake-up request via the WAKE pin. The Wake-up source

flag can be polled via the ERR_N pin in Normal mode (see Table 5). This flag is also set at

power-on and cleared when the transceiver leaves Normal mode.

7.2.6 Bus failure flag

The Bus failure flag is set if the transceiver detects a bus line short-circuit condition to

trying to drive the bus lines dominant. The Bus failure flag can be polled via the ERR_N

pin in Normal mode (see Table 5). This flag is cleared at power-on or when the transceiver

re-enters Normal mode.

7.2.7 Local failure flag

In Normal and Listen-only modes, the transceiver can distinguish four different local

failure events, any of which will cause the Local failure flag to be set. The four local failure

events are: TXD dominant clamping, TXD-to-RXD short circuit, bus dominant clamping

and an overtemperature event. The nature and detection of these local failures is

described in Section 7.3. The Local failure flag can be polled via the ERR_N pin in

Listen-only mode (see Table 5). This flag is cleared at power-on, when entering Normal

mode or when RXD is dominant while TXD is recessive, provided that all local failures

have been resolved.

7.3 Local failures

The TJA1043 can detect four different local failure conditions. Any of these failures will set

the Local failure flag, and in most cases the transmitter of the transceiver will be disabled.

7.3.1 TXD dominant clamping detection

A permanent LOW level on pin TXD (due to a hardware or software application failure)

would drive the CAN bus into a permanent dominant state, blocking all network

communications. The TXD dominant time-out function prevents such a network lock-up by

disabling the transmitter if pin TXD remains LOW for longer than the TXD dominant

40 kbit/s. The transmitter remains disabled until the Local failure flag has been cleared.

7.3.2 TXD-to-RXD short-circuit detection

A short-circuit between pins RXD and TXD would lock the bus in a permanent dominant

state once it had been driven dominant, because the low-side driver of RXD is typically

stronger than the high-side driver of the controller connected to TXD. TXD-to-RXD

short-circuit detection prevents such a network lock-up by disabling the transmitter. The

transmitter remains disabled until the Local failure flag has been cleared.