1-2-10 Implementations Of The Can Protocol; 1-2-11 Configuring A Can Network - Omron CJ1W-CORT21 Operation Manual

1-2-10 Implementations of the CAN Protocol

Overview
Communication is identical for all implementations of the CAN protocol. There are differences, how-
ever, with regard to the extent to which the implementation takes over message transmission from the
micro controllers which follow it in the circuit.
 CAN Controller with Intermediate Buffer
CAN controllers with intermediate buffer, formerly called basicCAN chips, have implemented as
hardware the logic necessary to create and verify the bitstream according to the protocol. However,
the administration of messages to be sent and received, acceptance filtering in particular, is carried
out only to a limited extent by the CAN controller.
 CAN Controller with Object Storage
CAN objects consist mainly of three components: identifier, data length code and the useful data.
CAN controllers with object storage, formerly called FullCAN, function like CAN controllers with
intermediate buffers. Additional they administer a certain number of objects. Where there are sev-
eral simultaneous requests to transmit objects over the bus, the CAN controllers determine, for
example, which object is to be transmitted first. They also carry out acceptance filtering for incoming
objects. The micro controller following the CAN controller has to administer only a few bits
(e.g. transmission request).
 CAN Slave Controllers for I/O Functions
As well as CAN controllers which support all functions of the CAN protocol there are also CAN
implementations possible which do not require a following micro controller. These CAN implementa-
tions are called SLIO (Serial Link I/O) acting as CAN slave units and having to be administered by a
CAN master unit.

1-2-11 Configuring a CAN Network

In order to operate a CAN network, each unit in the network needs to be configured. This process of
network and unit configuration involves the following procedures.
• Installing the physical network topology, i.e. installing User Defined CAN Units in the Controller sys-
tem, installing any other CAN unit in the network, and wiring the network.
• Configuring the bus parameters which define the baud rate and the bus timing parameter sample
point. Configuration for the User Defined CAN Unit is done either with the baud rate switches in the
front panel, or with message commands.
• Defining the configuration data, i.e. defining the process data, which will be exchanged between the
User Defined CAN Unit and other nodes on the CAN network.
• Defining the parameterization data for the User Defined CAN Unit which establishes the filtering of
message identifiers and the configuration of message buffers in the Controller.
• Parameterization of the User Defined CAN Unit with message commands issued from the User pro-
gram in the Controller.
CJ-series User Defined CAN Unit Operation Manual for NJ-series CPU Unit (W517)
1 Features and System Configuration
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