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6-4
Remote I/O Communications Performance
Section 6-1
Com
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P
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OUT Communications Cycle Time
OUT communications cycle time = (29 ms + 27 ms x number of allocated
data) + (7 ms
×
total allocated words in OUT Areas 1 and 2)
Refresh Processing
Time
The refresh processing time is the time required for the CPU Unit of the PLC
and the DeviceNet Master Unit to pass I/O information back and forth. The
cycle time of the PLC is affected as described below when a DeviceNet Unit is
mounted.
Note Refer to the operation manuals for the PLCs for details on the refresh pro-
cessing time and the PLC’s cycle time.
CS/CJ-series,
C200HX/HG/HE (-Z),
and C200HS PLCs
The following times for I/O refreshing are added to the cycle time of the PLC
when a Master Unit is mounted.
Note The number of allocated words is the total number of I/O area
words allocated to all of the slaves. Any unused areas within the al-
locations must be included. For example, if only node address 1
with a 1-word input and node address 5 with a 1-word input are
connected, the total number of words would be 5. When message
communications are performed, the number of words required for
message communications would have to be added to the above to-
tal number of words during the cycles in which message communi-
cations are processed.
6-1-3 Networks with More Than One Master
The communications cycle time, T
RM
, when there is more than one master in
the same network is described in this section. Here, a network with two mas-
ters is used as an example.
First, separate the network into two groups, slaves that perform remote I/O
communications with master A and those that perform remote I/O communi-
cations with master B.
Note Although for convenience, the slave are positioned in groups with the mas-
ters, in the actual network, the physical positions of the slaves will not neces-
sarily be related to the master with which they communicate.
Next, calculate the communications cycle time for each group referring to 6-1-
2 Communications Cycle time and Refresh Processing Time .
Item Processing time
I/O refresh DeviceNet Unit I/O Refresh Processing
CS/CJ-series or C200HX/HG/HE (-Z) PLCs
1.72 + 0.022 x number of allocated words (see note) ms
C200HS PLCs
2.27 + 0.077 x number of allocated words (see note) ms
Group B Group A
Master A
Slave a Slave b Slave c
Master B
Slave d Slave e Slave f
Slaves performing remote I/O
communications with master A
Slaves performing remote I/O
communications with master B