Manual VIPA System 100V
Chapter 2 Decentral block periphery CAN-Bus CANopen
HB100E - SM-CAN - Rev. 15/02
2-23
The parameter "PDO transmission type" fixes, how the sending of the
PDOs is initialized res. how received PDOs are handled:
Transmission Type Cyclical
Acyclical
Synchronous Asynchronous
0
x
x
1-240 x
x
254, 255
x
The transmission type 0 is only convenient for RxPDOs: The PDO is only
evaluated after the receipt of the next SYNC telegram.
At the transmission types 1-240, the PDO is sent res. expected cyclically:
after every n
th
SYNC (n=1...240). For the transmission type may not only be
combined in the network but also at one coupler, you may thus define e.g.
a fast cycle for the digital inputs (n=1), while the data of the analog inputs
are transmitted in a slower cycle (e.g. n=10). The cycle time (SYNC-Rate)
may be watched (object 0x1006), the coupler then switches its outputs to
error state at SYNC break-down.
The transmission types 254 + 255 are asynchronous or also event
triggered. At the transmission type 254 the event is proprietary, at 255 it is
defined in the device profile.
When choosing the event triggered PDO communication, you have to
regard, that there may be a lot of events at the same time and therefore
according delay times may occur until a low priority PDO can be sent.
You have also to avoid, that a often changing input with high PDO priority is
blocking the bus ("babbling idiot").
Via the parameter "Inhibit time" you may activate a "Send filter", that
doesn't lengthen the reaction time of the relatively first input alteration, but
is active at the directly following changes.
The inhibit time (send delay time) describes the time span you have
minimum to wait between the sending of two identical telegrams.
If you use the inhibit time, you may evaluate the maximum bus load and
therefore the latent time in a "worst case" scenario.
PDO transmission
type
Synchronous
Asynchronous
Inhibit time
