Rockwell Automation 1769-L23E-QB1B_L23E-QBFC1B_L23-QBFC1B CompactLogix Packaged Controllers Quick Start and User Manual - Manual (Page 226)

226 Publication IASIMP-QS010B-EN-P - October 2009
Chapter 3 Embedded I/O
Other Configuration
Parameters While each type of embedded I/O has type-specific parameters, for example
the embedded HSC has Operation and Storage mode parameters, there are
several configuration parameters that are common to both embedded I/O and
expansion I/O module configuration.
Use these tables that describe common configuration parameters as a
reference when configuring your emebedded I/O and expansion I/O
modules.
I/O Configuration Options
Configuration Option Description
Requested packet interval (RPI) The RPI specifies the interval at which data updates over a connection. For example, an input module
sends data to a controller at the RPI that you assign to the module.
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Typically, you configure an RPI in milliseconds (ms). The range is 0.2 ms...750 ms.
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If a ControlNet network connects the devices, the RPI reserves a slot in the stream of data flowing
across the ControlNet network. The timing of this slot may not coincide with the exact value of the
RPI, but the control system guarantees that the data transfers at least as often as the RPI.
Change of state (COS) Digital I/O modules use COS to determine when to send data to the controller. If a COS does not occur
within the RPI timeframe, the module multicasts data at the RPI.
Because the RPI and COS functions are asynchronous to the logic scan, it is possible for an input to
change state during program scan execution. If this is a concern, buffer input data so your logic has a
stable copy of data during its scan. Use the Synchronous Copy (CPS) instruction to copy the input data
from your input tags to another structure and use the data from that structure.
Communication format Many I/O modules support different formats. The communication format that you choose also
determines:
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data structure of tags.
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connections.
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network usage.
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ownership.
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returning of diagnostic information.
Electronic keying When you configure a module, you specify the slot number for the module. However, it is possible to
purposely or accidentally place a different module in that slot. Electronic keying lets you protect your
system against the accidental placement of the wrong module in a slot. The chosen keying option
determines how closely any module in a slot must match the configuration for that slot before the
controller opens a connection to the module. There are different keying options depending on your
application needs.