Remote I/O Communications Characteristics; Communications Cycle Time - Omron CJ1W-DRM21 Operation Manual

8 Communications Timing
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 DeviceNet 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:
• The DeviceNet Unit is operating with the scan list enabled.
• All of the required Slaves are participating in communications.
• No errors are being indicated at the DeviceNet Unit
• Messages aren't being produced in the Network (from another company's configurator, for example).
Additional Information
The values provided by these equations may not be accurate if another company's DeviceNet
Master or Slave is being used in the Network.
8-1-1

Communications Cycle Time

This section explains the communications cycle time and communications time per slave 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 communi-
cations 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 performed. The following explanation is for a network with one Master.
For networks with two or more Masters, refer to 8-1-3 More than One Master in Network.
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
8-2
Number of Slaves
: Communications cycle time: 500 kbit/s (ms)
: Communications cycle time: 250 kbit/s (ms)
: Communications cycle time: 125 kbit/s (ms)
CJ-series DeviceNet Units Operation Manual for NJ-series CPU Unit(W497)