Omron C200HW-CORT21, Руководство по эксплуатации

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Performance
Section 1-3
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1-3 Performance
The overall performance of C200HW-CORT21 depends on the performance
of the PLC interface and on the performance of the CAN interface. In the
next two sub-sections, these two factors will be described first. After that the
overall performance is described.
1-3-1 PLC cycle time
PLC cycle time The host PLC’s cycle time mainly depends on the size of the PLC program
and the I/O refresh times of all I/O Units on its backplane(s).
The size of the PLC program is application specific. Besides optimising the
PLC program, the program execution time can only be decreased by using a
faster CPU Unit.
I/O Refresh Time The total I/O refresh time depends on the types of Units that are mounted on
the backplane(s). Not all Units refresh the same amount of data.
The I/O refresh time of the C200HW-CORT21 depends on the number of
user defined CAN messages that have been received since the last I/O
refresh. Refer to section 4-6 for details about receiving user defined CAN
messages.
Calculation The I/O refresh time of the C200HW-CORT21 is:
t
IORF
= 1.0 + 0.11 x nm [ms]
where nm = number of received CAN messages (1 ~ 15)
Refer to the PLC Operation Manual for more detailed calculations of the PLC
cycle time.
1-3-2 CAN Interface
This sub-section describes the performance of the physical layer CAN and
the performance of the CAN interface of C200HW-CORT21.
The following figure depicts the transmission of CAN messages on the bus.
Message delay time Every message has a certain message delay time, that is mainly determined
by the size of the data field in the message. The implemented bit-stuff
mechanism (after every 5 consecutive equal value bits, a bit of the opposite
polarity is added) can lengthen the message delay time up to about 15%.
The following formulas give the minimum and maximum message delay time.