4 Message Communications
4-4
CJ-series User Defined CAN Unit Operation Manual for NJ-series CPU Unit (W517)
4-2
Unit Configuration and Control
In order to operate a CAN network, each unit in the network needs to be configured with software (user
program) configuration.
The total process of network and unit configuration involves:
•
Setting up the physical network topology
•
Setting up the bus parameters, which define the baud rate and the bus timing parameter sample
point
•
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 defines the filtering of mes-
sage identifiers and the configuration of message buffers in the CPU system.
For parameterization of the User Defined CAN Unit, memory areas and message parameterization
need to be configured upon power-up. The software configuration steps (user program) that must be
done after every ‘power on’ of the unit, to insure correct operation are:
(1) Setting memory area (buffer) allocations with command code 2902
(2) Setting parameters for sending messages with 11-bit identifier, or 29-bit identifier
(3) Setting parameters for receiving messages with 11-bit identifier, or 29-bit identifier
(4) Enable CAN communications, device variable
*_EnblCANComm
With this command code, the following items are configured:
•
send buffer location
•
send trigger location
•
receive buffer location
•
receive flag location
•
number of send and receive messages
One send or receive buffer occupies 5 words of CPU memory (Data Length Code (DLC) and the
8 bytes of data). One send trigger or receive flag occupies one bit of CPU memory. The number of
words occupied by all triggers or flags equals the number of send or receive messages divided by 16,
rounded up. Trailing padding bits are ignored.
Note
This command can be used only if communication has been disabled (by turning OFF device
variable
*_EnblCANComm
) and this disabling is confirmed by the unit (by an OFF state of
device variable
*_EnblComm
).
Additional Information
for more information about the Configure Memory Area
(2902) message command.
4-2-1
Configure Memory Areas (2902)
Summary of Contents for CJ1W-CORT21
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