BECKHOFF AX2000 CANopen communication profile - Manual (Page 24)

The definition of the PDO service and protocol can be found in DS301. Examples of the usage of
PDOs can be found in the application section of this documentation.
Basically, two types of PDOs can be distinguished, depending on the direction of transmission:
l Transmit-PDOs (TPDOs) (AX2xxx
Þ Master)
The TPDOs transmit data from AX2xxx to control system
(e.g actual value Objects, amplifier status).
l Receive-PDOs (RPDOs) (Master
Þ AX2xxx)
The RPDOs receive data from control system to AX2xxx
(e.g setpoints).
AX2000/2500 supports two independent PDO channels for each direction of transmission. The
channels are labeled by the channel numbers 1 to 4.
There are three parameters each for the configuration of each of the four possible PDOs, and they
can be set up through the corresponding SDOs:
1. Selection parameters, to select the two PDOs in each direction to be used for process
data operation from a number of possible PDOs (Objects 2600
h
to 2603
h
, 2A00
h
to 2A03
h
).
2. Mapping parameter, to determine which data are available (mapped) in the selected
PDO, and for entering the mapping of the PDO for the freely configured PDOs
(Nos. 37 to 40).
3. Communication parameters, that define whether the PDOs operate in synchronized mode,
or event-driven (Objects 1400
h
to 1403
h
, 1800
h
to 1803
h
).
Furthermore, individual bits of the TPDOs can be masked, so that an automatic generation of the
transmit-trigger can be controlled by individual bit event in TPDOs.
3.4.6.1 Transmission modes
The following PDO transmission modes are distinguished:
l Synchronous transmission
l Asynchronous transmission
The pre-defined SYNC Object is transmitted periodically (bus clock), to synchronize the drives. Syn-
chronous PDOs are transmitted within a pre-defined time window immediately following the SYNC
Object.
The transmission modes are set up with the aid of the PDO communication parameters.
24 CANopen for AX2000/2500
CANopen communication profile
07/2007
BECKHOFF
SYNC SYNC SYNC
Synchronous
Asynchronous
time
Synchronous
PDOs
Length
PDOs
Object
Window
Object Object