6-5
Remote I/O Communications Performance Section 6-1
Communications
Performance
The communications cycle time for the overall network when there are two
masters will be as follows:
T
RM
= T
RM-A
+ T
RM-B
Although this example uses a network with only two masters, the same
method can be used for any number of masters. Simply divide the network up
according to remote I/O communications groups and then add all of the com-
munications cycle times for the individual groups to calculate the communica-
tions cycle time for the overall network.
System Startup Time This section describes the system startup time for a Network, assuming that
the scan list is enabled and that remote I/O communications are set to start
automatically at startup. The system startup time is the delay from the time
that the Master Unit is turned ON or restarted until the time remote I/O com-
munications begin.
The system startup time when the Master Unit is set to start up immediately
after power supplies of all the slaves are turned ON is different from when the
Master Unit is restarted while communications are in progress. The startup
times are shown in the following table.
Sample Program The times described above are required for the DeviceNet system to start.
The sample program in this section shows how to use the Master Slave Sta-
tus to skip slave I/O processing until remote I/O communications have started.
Note Refer to the operation manual for the Master Unit for information on the Mas-
ter Status Area.
The following conditions apply to this sample program.
PLC: CS1 Series
Master Unit’s unit number: 00
Group BGroup A
Master A
Slave a Slave b Slave c
Master B
Slave d Slave e Slave f
Group A communications cycle time: T
RM-A
Group A communications cycle time: T
RM-B
Condition Slave's indicator status System startup
time
The master is started
immediately after slave
startup.
NS indicator is OFF or flashing green. 6 s
The master only is
restarted.
NS indicator is flashing red while the
master is OFF.
8 s
The slaves only are
restarted.
--- 10 s
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