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Chapter 10. PROFINET IO-Controller Operation
10.7.3 DO I/O for Remote IO Modules
In addition to the normal I/O updates that occur during the RXi CPU's scan, the application
program in the CPU can use the DO I/O function to access the I/O data associated with
Remote IO Modules on the PROFINET network during the logic portion of the CPU sweep.
The DO I/O function can obtain or update the most recent I/O data that is being consumed
from or published to the Remote IO Module by the PROFINET IO Controller. The DO I/O
function can also be used to obtain data associated with the PNC itself.
It is important to remember that the I/O data being read or written by the DO I/O function is
data currently being stored by the PNC in its memory. Executing a DO I/O function from the
CPU does not cause additional data to be produced or consumed on the PROFINET
NETWORK. Updates of the actual Remote IO Module I/O data occur during the configured
PROFINET cyclic scanning schedule. The DO I/O function provides the benefit of
immediately updating I/O data at the PNC, as opposed to waiting for the next normal RXi I/O
scan. The DO I/O function can also be used to obtain the PNC's latest input status data
values (refer to Section 10.8 PROFINET IO-Controller Diagnostics).
10.7.4 Scan Set I/O for Remote I/O Modules
The Scan Set I/O function of the RXi CPU requests the scanning of remote modules that are
members of a configured scan set. The Scan Set I/O function operates like a DO I/O function,
with the added ability to identify and group the modules to be scanned. Modules are grouped
according to their configured scan sets. As with the DO I/O function, the Scan Set I/O
function updates/consumes data stored in the local PNC; it does not directly update
IO-Devices in remote nodes.
10.7.5 I/O Defaults Operation
RXi CPU Defaults - Inputs
The CPU defaults input data from remote I/O modules under the following conditions:
The CPU defaults the input values of an input module based on the input default state
configured for the I/O Device. Inputs may be configured to either Hold Last State or Force Off
(zero).
If a PNC loses connections to an I/O device, the following actions occur:
1. The CPU defaults the input values of all input modules assigned to it within the
2. The PNC logs a Loss of Device fault in the CPU's I/O fault table.
3. The I/O point fault contacts for the I/O references and variables associated with the
RXi CPU Defaults - Outputs
Outputs default when the CPU is no longer providing the data (for example when CPU has IO
disabled). I/O modules control their own output defaults based on either their configuration or
on a fixed output default behavior (typically 0) if the module's output default behavior is not
configurable.
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the remote module signals its input data is no longer valid (for example due to local
module fault)
the remote module is removed from the network
the remote module loses power or fails
the PROFINET network connection (Application Relationship) associated with the input
data is lost.
IO-Device.
IO-Device are set to the faulted state (if point faults are enabled on the CPU).
PACSystems* RXi Distributed IO Controller User Manual
GFK-2816F
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