Physical Layer - CAN System Engineering - page 116

Fig. 2.53 Application circuit for partial networking HS-CAN transceiver E520.13
length of the CAN identifier is 11 bits and the length of the CAN data field comes
to 64 bits.
Figure 2.54 depicts the selective wake-up of a control unit equipped with the de-
vice E520.13 by means of a WUF. At the start of the measurement cycle, the control
unit is in partial network mode. Shown are the respective signal sequences at the two
bus pins CAN high (CAN_H) and CAN low (CAN_L) and at the pin INH through
which the wake-up call is signalled to the controller's internal power supply. The up-
per subfigure a) shows a detail of the bus traffic, where several hundred data frames
with pseudo-arbitrary content are transmitted. The control unit in partial network
mode “listens” to the bus communication and is capable of receiving, decoding and
analysing the data frames in a reliable and robust way. The control unit remains in
partial network mode. Only when the controller-specific WUF, consisting here, e.g.
of the CAN identifier 0xFF and the CAN data field 0 × 00 00 00 00 00 00 00 FF, is
transmitted on the data bus, the wake-up call is initiated by changing from low to
high at the INH pin to get the controller out of partial network mode. The data frame
setting off the wake-up event is shown enlarged in the lower subfigure (Fig. 2.54 b).
A very short delay in the range of a few tens of microseconds between WUF and
state-change at the INH pin can be observed.