Civil Engineering Reference
In-Depth Information
The most important transceiver modes are:
• Sleep mode
• Stand-by mode
• Normal mode
• Go-to-sleep mode
Sleep Mode
The fault-tolerant low-speed CAN transceiver (according to ISO 11898-3) and the
high-speed CAN transceiver (according to ISO 11898-5) with remote wake func-
tion can be permanently supplied and have a sleep mode to reduce the current
consumption below 30 µA. In this mode, the pin Inhibit (INH) is switched off. In
the transceiver itself, the receiver is active with a very low current consumption
to monitor CAN communication on the bus. A valid differential signal on the bus
wakes the transceiver up, sets the transceiver in standby mode and switches on the
INH pin. If a local wake pin is implemented, the transceiver can be woken up with
level changes on this pin too.
Standby Mode
The standby mode is an intermediate mode after a transceiver wake up. The reasons
for a wake-up can be:
• Power-up
• Level change on local wake pin
• Remote bus wake-up
In standby mode, the transmitter is blocked and set to recessive to guarantee no
disturbance on the bus during microcontroller ramp-up. Depending on the imple-
mentation, the wake-up source is flagged. Normally, a remote wake-up is flagged
on the pin RxD with a permanent dominant signal. A mode change in normal mode
resets this flag. In standby mode, the INH pin (if available) is set to high. An INH-
controlled voltage regulator will be switched on.
Normal Mode
In normal mode, the transceiver transmits and receives data. The transceiver can
be set in normal mode via the mode pin EN. This mode pin is controlled from the
microcontroller. In some transceiver products, a TxD-dominant time-out protec-
tion is implemented too. In case of a permanent dominant signal on the pin TxD,
the bus is blocked and the communication on the bus is corrupted. After a defined
time, the TxD-dominant time-out protection will set the transmitter to recessive and
the communication on the bus can be continued. The release of this TxD-dominant
