110
Remote I/O Communications Characteristics
Section 6-1
6-1
Remote I/O Communications Characteristics
This section describes the characteristics of remote I/O communications
when a DeviceNet PCI Board is used with OMRON Slaves. Use this section
for reference when planning operations that require precise I/O timing.
The equations provided here are valid under the following conditions:
1,2,3...
1.
All of the required Slaves are participating in communications.
2.
No errors have occurred in any of the nodes in the network.
3.
There are no I/O refreshing requests or command requests from the com-
puter to the board.
Note
The values provided by these equations may not be accurate if the conditions
described above are not satisfied.
6-1-1
Communications Cycle Time
The communications cycle time is the time from the completion of a Slave’s
remote I/O communications processing until remote I/O communications with
the same Slave are processed again. The communications cycle time is used
to calculate the maximum I/O response time.
The communications cycle time depends on a variety of factors such as the
number of Masters in the Network and on whether or not message communi-
cations are being performed. The following explanation is for a network with
one Master. For networks with two or more Masters, refer to
.
Communications Cycle
Time Graph
The following graph plots the communications cycle time against the number
of Slaves, for a mixture of 16-output point Slaves and 16-input point Slaves.
Bit-strobe input and poll connection output are used.
Equations for Calculating
Communications Cycle
Time
Use the equations shown below to calculate the communications cycle time
(T
RM
) for a network with one Master. (The minimum communications cycle
time is actually 2 ms even if the result of this calculation is less than 2 ms.)
T
RM
=
Σ
(Communications time per Slave)
+ High-density Unit processing time
+ Explicit message processing time
+ COS/Cyclic connection communications time [ms]
+ 0.01
×
N + 1.0 [ms]
2
0
10
20
30
40
50
60
4
6
8 10 12 14 16 18 20 22 24 26 28 30 32
No. of Slaves
Communications cycle time (500 kbps) [ms]
: Communications cycle time (250 kbps) [ms]
: Communications cycle time (125 kbps) [ms]
Communications cycle time (ms)
34 36 38 40 42 44 46 48 50 52 54 56 58 60 62
Summary of Contents for DeviceNet 3G8F7-DRM21-E
Page 1: ...OPERATION MANUAL Cat No W381 E1 02 3G8F7 DRM21 E DeviceNet PCI Board ...
Page 2: ...3G8F7 DRM21 E DeviceNet PCI Board Operation Manual Revised July 2005 ...
Page 3: ...iv ...
Page 5: ...vi ...
Page 29: ...12 Preparation for Operation Section 1 8 ...
Page 67: ...50 PC Watchdog Timer Management Function Section 3 11 ...
Page 115: ...98 Maintenance API Functions Section 4 7 ...
Page 131: ...114 Remote I O Communications Characteristics Section 6 1 ...
Page 145: ...Index 128 ...
Page 147: ...130 Revision History ...
