Omron SYSMAC CJ1W-EIP21 - Manual (Page 314)

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I/O Response Time in Tag Data Links Section 10-3
(3) Packet Interval (RPI)
This is the communications refresh cycle set for each connection using the
Network Configurator. In this system, it is the refresh cycle for connection 1
(10 ms), which includes W000.01.
(4) Network Transmission Delay Time
This is the total of the send processing delay, receive processing delay,
switching hub delay, and cable delay. Refer to 10-1-3 Network Transmission
Delay Time for details on the calculation formula for network delay time. In this
system, it is 5.2 ms.
(5) Node 2 (PLC #2) Receive Data Processing Time
This is the time to transfer the data received by the EtherNet/IP Unit or CJ2H
built-in port to the memory area in the CPU Unit. Receive data is transferred
in the order that it is received, but if the amount of data that can be processed
in one transmission is exceeded, multiple cycles are required to transfer the
data. Also, data transmission is performed only once per CPU Unit cycle.
Therefore, if data transfer has ended in the cycle in which data is received, the
start of transmission for received data will be delayed by one CPU Unit cycle
time.
In this system configuration, data transfer is performed a maximum of three
times based on the data size of node 2 (PLC #2) to transfer received data for
node 1 (PLC #1) and node address 3 (PLC #3). Also, the cycle time of PLC #2
is 15 ms, the effect on the CPU Unit cycle time is 2.3 ms, and the data pro-
cessing time for the EtherNet/IP Unit or CJ2H built-in port is 6.15 ms. The
number of data transmissions is thus calculated as 3. In addition, the number
of data transmissions is calculated as a maximum of 4 (3 + 1) because it is
necessary to consider a delay of one CPU Unit cycle time in transferring
received data.
D
Number of data trans-
missions
A
10 m sec >
C
6.15 m sec
To meet the conditions, the number of trans-
missions is the same as
B
.
2
Total:
(2) Send data process-
ing time
CPU Unit cycle time of A PLC #1 × D Num-
ber of data transmissions
20 m sec
Delay item Calculation formula Max. delay time
A Send processing delay 10 m sec × (15-10 msec/100)% 1.49 msec
B
Cable delay 545 nsec + 50 m/100 272.5 nsec
C Switching hub delay 2 msec + Approx. 0.7 msec 2.7 msec
D Receive processing
delay
1 + (0 connection × 0.043) 1.0 msec
Total:
(4) Network Transmission
Delay Time
A
+
B
+
C
+
D
5.2 msec
Item Calculation formula Time
A CPU Unit cycle time --- 15 msec
B
Number of transmis-
sions based on the data
size
Number of data transmission words (15,648
words)
÷ 6,432 words (using a CJ2 CPU
Unit)
3
C EtherNet/IP Unit data
processing time
0.0008 × 6,432 + 1.0 (Maximum number of
transmission words per cycle)
6.15 msec
Item Calculation formula Time