Baumuller b Maxx Series - 5.5 Process data (PDO)

Data Exchange and Parameterization
Application Manual POWERLINK Controlled Node
Document no. 5.13013.04
37
of 80
5
5.5 Process data (PDO)
Process data objects are unconfirmed frames that are optimized for the exchange of data
with real-time requirements. There are two kinds of PDOs, differing in the direction of the
data transmission from the perspective of the device. The POWERLINK Controlled
Node for b maXX 4000 controllers supports a transmit PDO (TPDO) as well as a receive
PDO (RPDO). Up to eight objects can be transmitted in each PDO.
The PDO communication in PO
WERLINK is executed by synchronous PReq respective-
ly PRes frames. In the synchronous phase the MN sends
the PollRequest (PReq) as uni-
cast frame. The corresponding C
N sends the PollResponse (PRes) as broadcast.
The format of the data exchange has to be defin
ed before starting the communication be-
tween sender and receiver (mapping). The send
ing and receiving of PDOs can be initiat-
ed in different kind of ways.
NOTE!
All objects, which were configured in the PDOs are transmitted between the
POWERLINK Controlled Node and the b maXX 4000 controller as cyclic data (also
see ZCommu
nication flow– from page 17). As the cyclic data transmission is only
made in the state of NMT_CS_OPERATIONAL
, the communication monitoring in
ProDrive BACI should be only in this status be activated (timeout for cyclic commu-
nication P0
836 BACI).
5.5.1 Frame structure PReq and PRes
The structure of the PollRequest (PReq) frame is as follows:
Bit offset
Byte offset 7 6 5 4 3 2 1 0
0 Message Type = PReq (0x03)
1 Destination = Node ID of the CN
2 Source = Node ID of the MN (0xF0)
3 reserved
4 res res MS res res EA res RD
5 reserved
6 PDOVersion
7 reserved
8 ... 9 Size (Size of the process data in byte)
10 ... n Payload
MS (Multiplexed Slot) 
EA (Exception Acknowledge) 
RD (Ready)