Civil Engineering Reference
In-Depth Information
The mode transitions 1, 3 and 5 are well known from the ISO 11898-5 transceiv-
ers. New are the transitions 2, 4, 6 and 7.
For transition 2 (mode change into low-power mode with selective wake func-
tion) the transceiver must be checked, if the oscillator is synch, and the CAN frames
were detected from the transceiver correctly. Before the transceiver can be set into
low-power mode, the dedicated WUF must be sent to the transceiver. After this op-
eration proceeds successfully, the transceiver can be set into this low-power mode.
If the transceiver has detected a WUF, the transceiver changes into standby mode
and ramps up the ECU (transition 4). If there is no communication on the bus in
low-power mode with selective wake, the transceiver will change into sleep mode
(transition 6s) and returns after the communication on the bus starts again (transi-
tion 7). The advantage from this approach is a very low current consumption in
low-power mode. The disadvantage is the fact that only one dedicated WUF wakes
up the ECU. In addition, the long ramp-up time is a disadvantage of this system. A
first implementation from Infineon can be found on the TLE9267QX.
2.5.3.5
Trx_Standby Mode with Activated Selective Wake-Up Function
In this mode:
• RxD is decoupled from the receiver and RxD is set to logical 1.
• Transmitter is deactivated.
• VBIAS (voltage source for VCC/2) is active to improve the signal integrity.
• INH is logical “1” (to activate the voltage regulator).
• The WUF-detection unit is active.
• Tsilence timer is active.
The transceiver enters this mode after a valid WUF is detected.
2.5.3.6
Trx_Sleep Mode with Activated Selective Wake-Up Function
In this mode:
• RxD is decoupled from the receiver (RxD is logical “1”).
• Transmitter is deactivated.
• VBIAS (voltage source for VCC/2) is active to stabilize the signal integrity.
• INH is logical “0” (to switch off the voltage regulator and the rest of the ECU).
• WUF-detection unit is active.
• Tsilence timer is active.
In this mode, the microcontroller is unpowered or in stop mode. After the detec-
tion of a WUF, the transceiver changes into the Trx_Standby mode with selective
wake-up function and sets the INH pin to logical “1”. With “1” on INH, the voltage
regulator is activated and powers the microcontroller. After ramp-up of the micro-
controller, the software is able to set the transceiver in normal mode. Through serial
peripheral interface (SPI) of the transceiver, the wake-up source can be read out.
