Table of Contents
Advertisement
Remote I/O Communications Performance
PLC
Master Unit
Input
Input
T
T
IN
RM
Note
6-1-2
Communications Cycle time and Refresh Processing Time
Communications Cycle Time
Communications Cycle Time Equations
The minimum I/O refresh time can be calculated as follows:
T
= T
+ T
+ (T
MIN
IN
RT-IN
Maximum I/O Response Time
The maximum I/O response time occurs under the conditions shown in the
following diagram.
Program
Program
execution
execution
T
PLC
T
:
ON/OFF delay time of the input slave (0 used as minimum value)
IN
T
:
ON/OFF delay time of the output slave (0 used as minimum value)
OUT
T
:
Communications time for entire network
RM
T
:
Cycle time of PLC
PLC
T
:
DeviceNet Unit refresh time at PLC
RF
Refer to the operation manuals for the slaves for the input slave ON/OFF
delay times and the output slave ON/OFF delay times. Refer to 6-1-2 Com-
munications Cycle time and Refresh Processing Time and to the operation
manual for the PLC for the PLC cycle time.
The maximum I/O refresh time can be calculated as follows:
T
= T
+ 2 x T
MAX
IN
RM
This section describes the communications cycle time and refresh processing
time, which are required to calculate various processing times for DeviceNet.
The communications cycle time is the time from the completion of a slave's
I/O communications processing until I/O communications with the same slave
are processed again. The communications cycle time is the maximum com-
munications cycle time T
The equations used to calculate the communications cycle time are described
here.
Total communications cycle time = IN communications cycle time + OUT com-
munications cycle time.
■ IN Communications Cycle Time
IN communications cycle time = (39 ms + 8 ms x number of allocated data) +
(6 ms × total allocated words in IN Areas 1 and 2)
− T
) + T
+ T
PLC
RF
RT-OUT
Program
execution
T
T
T
PLC
RF
RM
+ 2 x T
+ T
+ T
PLC
RF
OUT
+ T
.
IN
OUT
Section 6-1
OUT
T
OUT
6-3
Advertisement
Chapters
Table of Contents
