Basics POWERLINK
Application Manual POWERLINK Controlled Node
Document no. 5.13013.04
11
of 80
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Ethernet frame The Ethernet frame consists of a header and the data payload. The header consists of
the destination and the source MAC address as well as of the Ethertype field that contains
some control information. The Ethernet payload field, including the POWERLINK frame,
contains at least 46 and up to 1500 bytes. Concluding, the correctness of the frame is en-
sured by means of a checksum.
Target MAC Source MAC
Ether
type
User data (POWERLINK) Pad CRC
48 bit 48 bit 16 bit >24 bit 32 bit
R
Message
Type
Target
node
Source
node
User data
1 bit 7 bit 8 bit 8 bit
POWERLINK
frame
The POWERLINK frame consists of a header and the actual data payload as well. The
header consists of a reserved-bit, the message type, the destination node and the source
node. The following message types are defined.
Message type ID Designation Use Transfer type
SoC 0x01 Start of Cycle Defines the start of a
new cycle
Multicast
PReq 0x03 Poll Request Ask for cyclic data of
the CN
Unicast
PRes 0x04 Poll Response Send current cyclic
data of the CN
Multicast
SoA 0x05 Start of
Asynchronous
Signalize the start of
the asynchronous
phase
Multicast
ASnd 0x06 Asynchronous
Send
Sending of asynchro-
nous data
Multicast
Determinism The various participants in the network, the Controlled Nodes (CN), are controlled by a
specific
participant, the Managed Node (MN), and are only allowed to send, if they are
asked to by the MN.
The PO
WERLINK cycle is divided into a synchronous and a asynchronous phase. At the
beginning of the synchronous phase, the MN sends the SoC Frame. Subsequently, each
single node is enquired by the MN with a PReq and responds with the PRes. After the
cyclic phase, the MN starts the asynchronous phase with the sending of the SoA frame.
A node determined by the MN can transmit acyclic data by means of a ASnd frame.
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