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5-9
5 Communications Timing
CJ-series User Defined CAN Unit Operation Manual for NJ-series CPU Unit (W517)
5
-1 Perfo
rmanc
e
5
5-
1-7 R
eception of C
A
N Message
s
Sending messages with SM1, SM2 or SM3 differs from direct sending CAN messages. There is no
delay between the start of ‘program execution’ and passing the message to the User Defined CAN
Unit.
The User Defined CAN Unit can store up to 15 received messages in its internal buffer, the receive
queue. These messages in the receive queue are filtered (according to the configuration of the input
buffers) and transferred to the CPU. It may take several CPU cycles to filter and transfer a CAN mes-
sage to the CPU.
The performance of the unit depends on the number of input and output buffers. If several input and/or
output buffers are used, the unit will require more time for processing. Limiting the number of input
and/or output buffers can increase performance.
The CPU cycle time also influences the performance. If the CPU cycle time is long, the receive queue
in the unit may overflow. Refer to the
NJ-series CPU Unit Software User’s Manual
(Cat. No. W501) for
more info.
Transmitting With Send Mode
5-1-7
Reception of CAN Messages
CPU
CORT21
Bus
Output node
t
RF
t
RF
t
UDC
: The transmission time of a user defined CAN message
t
RF
: The I/O Refresh time
t
PE
: The Program Execution time
UDC
t
t
PE
SM1, SM2, SM3
Summary of Contents for CJ1W-CORT21
Page 2: ......
Page 140: ...Appendices A 6 CJ series User Defined CAN Unit Operation Manual for NJ series CPU Unit W517...
Page 141: ...Index 1 CJ series User Defined CAN Unit Operation Manual for NJ series CPU Unit W517 I Index...
Page 144: ...Index 4 CJ series User Defined CAN Unit Operation Manual for NJ series CPU Unit W517 Index...