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 The following graph shows communications cycle time for the number of

Time Graphslaves when there are both 16-point output and 16-point input slaves. Inputs: Bit strobe, Outputs: Poll connection

Communications cycle time (ms)

Number of Slaves

:Communications cycle time: 500 kbps (ms)

:Communications cycle time: 250 kbps (ms)

:Communications cycle time: 125 kbps (ms)

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Omron CS1W-DRM21, CJ1W-DRM21 Remote I/O Communications Characteristics, Communications Cycle Time and Refresh Time