ifm
System Manual
ecomat
mobile
PDM360NG (CR1080, CR1081, CR9042) Target V01
2011-07-28
CAN in the PDM360
General about CAN
159
9.1.1
Topology
1244
The CAN network is set up in a line structure. A limited number of spurs is allowed. Moreover, a ring
type bus (infotainment area) and a star type bus (central locking) are possible. Compared to the line
type bus both variants have one disadvantage:
In the ring type bus all control devices are connected in series so that the complete bus fails if one
control device fails.
The star type bus is mostly controlled by a central processor as all information must flow through
this processor. Consequently no information can be transferred if the central processor fails. If an
individual control device fails, the bus continues to function.
The linear bus has the advantage that all control devices are in parallel of a central cable. Only if this
fails, the bus no longer functions.
NOTE
The line must be terminated at its two ends using a terminating resistor of 120
to prevent corruption
of the signal quality.
The devices of
ifm electronic
equipped with a CAN interface have no terminating resistors.
The disadvantage of spurs and star-type bus is that the wave resistance is difficult to determine. In the
worst case the bus no longer functions.
For a high-speed bus (> 125 kbits/s) 2 terminating resistors of 120
(between CAN_HIGH and
CAN_LOW) must additionally be used at the cable ends.
