Omron CJ1W-DRM21, Operation Manual

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8-3
8 Communications Timing
CJ-series DeviceNet Units Operation Manual for NJ-series CPU Unit(W497)
8-1 Remo
te I/
O Co
mm
u
n
ication
s
Characteristics
8
8-1
-1 Comm
unications Cycle T
ime
z
Communications Cycle Time Calculation
Use the equations shown below to calculate the communications cycle time (T
RM
) for a network with
one Master. Note that if the result of this calculation is less than 2 ms, the actual communications
cycle time will be 2 ms.
T
RM
=
Σ
(Communications time per Slave)
+ High-density Unit processing time
+ Explicit message communications time
+ COS/Cyclic connection time (ms)
+ 0.01
×
N + 1.0 [ms]
Communications Time per Slave:
This is the communications time required for a single Slave.
"
Σ
(Communications time per Slave)" represents the total of the "Communications time per Slave"
for all the Slaves in the network.
High-density Unit Processing Time:
3.5 ms
This is added if there are any Slaves in the network that use at least 8 bytes for input, output, or
both.
Explicit Message Communications Time:
(0.11
×
T
B
)
×
n [ms]
The explicit message communications time is added as a delay time when explicit communications
(sending or receiving) are performed.
n= Number of explicit messages (both sending and receiving) that occur simultaneously within one
CPU Unit task period of CPU Unit
T
B
= The baud rate factor
(500 kbit/s: T
B
= 2; 250 kbit/s: T
B
= 4; 125 kbit/s: T
B
= 8)
COS/Cyclic Connection Time:
{(0.05+0.008
×
S)
×
T
B
}
×
n (ms)
The COS/cyclic connection time is added as a delay time when COS/cyclic communications are per-
formed.
S: Total number of inputs and outputs in the COS/cyclic connection (bytes)
T
B
: The baud rate factor
(500 kbit/s: T
B
= 2; 250 kbit/s: T
B
= 4; 125 kbit/s: T
B
= 8)
n: Number of nodes occurring simultaneously within 1 communications cycle time in the COS/Cyclic
connection
N: Number of Slaves
The communications time per Slave is the communications time required for a single Slave.
The following equations show the communications time/Slave (T
RT
) for each kind of Slave Unit.
The communications time for each slave is not related to the type of connection (protocol) used by the
slave.
z
Output Slaves with Less Than 8 Bytes of Output
T
RT
= 0.016
×
T
B
×
S
OUT1
+ 0.11
×
T
B
+ 0.07 [ms]
S
OUT1
: The number of Output Slave output words
T
B
: The baud rate factor
(500 kbit/s: T
B
= 2; 250 kbit/s: T
B
= 4; 125 kbit/s: T
B
= 8)
Communications Time/Slave