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Remote I/O Communications Characteristics Section 8-1
8-1 Remote I/O Communications Characteristics
This section describes the characteristics of remote I/O communications
when the DeviceNet Unit is used as a master in combination with OMRON’s
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. The DeviceNet Unit is operating with the scan list enabled.
2. All of the required Slaves are participating in communications.
3. No errors are being indicated at the DeviceNet Unit
4. Messages aren’t being produced in the Network (from another company’s
configurator, for example).
Note The values provided by these equations may not be accurate if another com-
pany’s Master or Slave is being used in the Network.
8-1-1 Communications Cycle Time and Refresh Time
This section explains the communications cycle time, communications time
per slave, and refresh time required for calculating processing time by the
DeviceNet Unit.
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 the number of Masters in the
Network and on whether or not message communications are being per-
formed. The following explanation is for a network with one Master. For net-
works with several Masters, refer to More than One Master in Network in the
following section.
Communications Cycle
Time Graph
The following graph shows communications cycle time for the number of
slaves when there are both 16-point output and 16-point input slaves.
Inputs: Bit strobe, Outputs: Poll connection
Number of Slaves
: Communications cycle time: 500 kbps (ms)
: Communications cycle time: 250 kbps (ms)
: Communications cycle time: 125 kbps (ms)
Communications cycle time (ms)