Image Processing Reference
In-Depth Information
Application-specific
event or
timer expired
PDO
Write PDO ind.
Write PDO req.
Read PDO req.
rtr
Read PDO ind.
PDO
Read PDO con.
Read PDO res.
SYNC
Write SYNC ind.
Write SYNC ind.
PDO
Write PDO ind.
Write PDO req.
PDO producer
PDO consumer(s)
FIGURE .
Transmission modes.
15.6.3.2 PDO Configuration
Details about the way any specific PDO is transmitted over the CAN network are defined through
the PDO communication parameter. It includes a lot of information and, in particular:
•
CAN-ID used for the CAN frame that embeds the PDO.
•
Transmission type, as specified above.
•
Inhibit time (expressed as a multiple of µs), which is the shortest time that must
elapse between any two transmissions of the PDO. This is useful to prevent high pri-
ority messages from hogging all the available bandwidth, thus ruling out lower priority
communications.
•
Event timer (expressed as a multiple of ms), that is the maximum time between two
subsequent transmissions of the same PDO; it can be used to enforce a minimum refresh
rate for slowly changing values.
•
SYNC start value that is used as a displacement for multiplexing synchronous PDOs
whose periodicity is larger than the cycle time.
Communication parameters for RPDOs and TPDOs are stored in the OD in entries
h
-FF
h
and
h
-FF
h
,respectively.
The PDO mapping parameter, instead, specifies how the information stored in the entries of
theODarecombinedtobuildthepayloadofaTPDO(or,equivalently,todecodeanRPDO).
PDO mapping is useful to improve the protocol efficiency: in fact, it enables several signals in the
