Product data

UJA1167 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 2 — 18 April 2014 20 of 60
NXP Semiconductors
UJA1167
Mini high-speed CAN system basis chip with Standby/Sleep modes &
watchdog
The CAN transceiver is in Active mode when:
• the UJA1167 is in Normal mode (MC = 111) and the CAN transceiver has been
enabled by setting bits CMC in the CAN control register to 01 or 10 (see Table 14
)
and:
– if CMC = 01, the voltage on pin V1 is above the 90 % undervoltage threshold
– if CMC = 10, the voltage on pin V1 is above the V1 reset threshold
If pin TXD is held LOW (e.g. by a short-circuit to GND) when CAN Active mode is selected
via bits CMC, the transceiver will not enter CAN Active mode but will switch to or remain in
CAN Listen-only mode. It will remain in Listen-only mode until pin TXD goes HIGH in
order to prevent a hardware and/or software application failure from driving the bus lines
to an unwanted dominant state.
In CAN Active mode, the CAN bias voltage is derived from V1.
The application can determine whether the CAN transceiver is ready to transmit/receive
data or is disabled by reading the CAN Transceiver Status (CTS) bit in the Transceiver
Status Register (Table 15
).
6.7.1.2 CAN Listen-only mode
CAN Listen-only mode allows the UJA1167 to monitor bus activity while the transceiver is
inactive, without influencing bus levels. This facility could be used by development tools
that need to listen to the bus but do not need to transmit or receive data or for
software-driven selective wake-up. Dedicated microcontrollers could be used for selective
wake-up, providing an embedded low-power CAN engine designed to monitor the bus for
potential wake-up events.
In Listen-only mode the CAN transmitter is disabled, reducing current consumption. The
CAN receiver and CAN biasing remain active. This enables the host microcontroller to
switch to a low-power mode in which an embedded CAN protocol controller remains
active, waiting for a signal to wake up the microcontroller.
The CAN transceiver is in Listen-only mode when:
• the UJA1167 is in Normal mode and CMC = 11
The CAN transceiver will not leave Listen-only mode while TXD is LOW or CAN Active
mode is selected with CMC = 01 while the voltage on V1 is below the 90 % undervoltage
threshold.
6.7.1.3 CAN Offline and Offline Bias modes
In CAN Offline mode, the transceiver monitors the CAN bus for a wake-up event, provided
CAN wake-up detection is enabled (CWE = 1). CANH and CANL are biased to GND.
CAN Offline Bias mode is the same as CAN Offline mode, with the exception that the CAN
bus is biased to 2.5 V. This mode is activated automatically when activity is detected on
the CAN bus while the transceiver is in CAN Offline mode. The transceiver will return to
CAN Offline mode if the CAN bus is silent (no CAN bus edges) for longer than t
to(silence)
.
The CAN transceiver switches to CAN Offline mode from CAN Active mode or CAN
Listen-only mode if: