Transmission Of User Defined Can Messages; Reception Of User Defined Can Messages - Omron C200HW-CORT21-V1 Operation Manual

Performance

2-3-3-2 Transmission of user defined CAN messages

2-3-3-3 Reception of user defined CAN messages

The following figure shows the sequence of transmitting a user defined CAN
message.
PLC
CORT21-V1
Bus
Output node
t
RF
t : The transmission time of a user defined CAN message
UDC
t
: The I/O Refresh time
RF
t
: The Program Execution time
PE
Refer to the PLC Operation manual for the execution time of an IOWR PLC
instruction. After the content of the IOWR is transferred to the C200HW-
CORT21-V1, the Unit immediately relays the contained message to the CAN
transmission interface. The actual transmission delay of the message
depends on the bus load and the message priority (identifier). Refer to
section 2-3-2 for the message delay time on the bus. The time required for
an output to be set or a value in the Output Node to be changed depends on
the characteristics of the Output node.
The minimum time between the execution of the IOWR instruction in the PLC
program and the message being transmitted on the bus is 0.5 ms.
In order to receive user-defined CAN messages, an IOWR instruction must
be executed to configure the Unit regarding :
•
which messages to receive (filter identifiers by range and/or mask)
•
which PLC memory locations to copy the receive messages to.
This only needs to be done once, and only needs to be repeated to change
the filter and/or PLC memory allocation. Immediately after the execution of
the IOWR instruction, the Unit is ready to receive messages.
The C200HW-CORT21-V1 can to store up to received 15 messages in its
internal buffer. All stored messages are transferred to the PLC during the
next I/O refresh. Therefore, the maximum delay time in the message
reception is one PLC cycle.
The maximum message rate that can be successfully received therefore
depends strongly on the PLC cycle time. e.g. if the PLC cycle time is 20 ms,
the maximum message rate is 15 messages/20 ms = 750 messages/second.
IOWR
t
UDC
t t
PE RF
Section 2-3
29