Can Network Protocol - Anybus Communicator CAN PROFINET IRT 2.32 User Manual

Description
2.5

CAN Network Protocol

2.5.1 General
The CAN protocol is message-based and can exchange up to 8 bytes of data in each message.
It is a transparent protocol, meaning that it only acts as a data carrier, and it is up to each appli-
cation to define and interpret the data content of the messages.
Data is exchanged using frames. Each frame has a unique identifier for the data it exchanges,
which also represents the message priority. Anybus Communicator CAN supports both 11-bit
(CAN 2.0A) and 29-bit (CAN 2.0B) identifiers, selected in the configuration.
CAN is essentially a produce-consume protocol, where all nodes listen to all messages. The de-
vices recognize what data to collect by the identifier in the CAN frame. Anybus Communicator
CAN is also able to act as a network master and issue queries that demand responses. Both
methods can be used within the same configuration.
2.5.2 Message Types
Anybus Communicator CAN features three CAN message types: Query-Response, Produce,
and Consume. These message types only specify the basic communication model, not the ac-
tual CAN protocol. All three message types can be used in the same configuration.
Query-Response
The Anybus Communicator CAN here acts as a master on the CAN subnetwork, and communi-
cation takes place in a query-response fashion. The gateway sends a query and expects a re-
sponse within a specified timeout.
Control System
Fig. 5 Query-Response messaging
Produce and Consume
Here there is no master-slave relationship between the Anybus Communicator CAN and the
subnetwork nodes. Any node, including the gateway, may both produce and consume mes-
sages. Nodes do not have to respond to messages, or wait for a query in order to send one.
The consumed data can be accessed from the higher level network, and vice versa.
Control System
Fig. 6 Produce and Consume messages
®
Anybus Communicator ™ CAN PROFINET
Anybus Communicator
Anybus Communicator
CONSUME
Node 1
PRODUCE
CONSUME
®
IRT (2.32) User Manual
Subnetwork
QUERY
RESPONSE
BROADCAST
QUERY
RESPONSE
Subnetwork
PRODUCE
CONSUME
PRODUCE
9 (30)
Node 1
Node 2
Node 2
Node 3
SCM-1202-035 1.0