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Rockwell Automation Publication 1715-UM001J-EN-P - December 2020
Chapter 8 Using SIL 2 Add-On Instructions with 1715 Redundant I/O Modules
Add-On Instruction Outputs
The Add-On Instructions generate these outputs.
Input_Data
This is the raw data from the 1715 module. You must point to this tag when
configuring the Add-On Instruction.
Module_RPI
Enter this value manually from the module properties. Use the exact value to
optimize system bandwidth.
Reset
The reset function requires a LO to HI transition of this tag. It resets faults
and directs the ControlLogix controller to stop transferring the safe state
data and start transferring the actual data, if the SIL 2 check data is verified.
This tag is also sent to the 1715 output modules so that outputs can be reset
from the safe state.
Table 43 - Add-On Instruction Inputs
Input
Description
Table 44 - Add-On Instruction Outputs
Output
Description
Data Valid
This value is HI if the Add-On Instruction is moving the input data to the
Reconciled Input Data tag without substituting safe state values. This value
remains HI if packets are being discarded but the CRTL has not timed out.
During this time, the reconciled input data is not updated and data is no
longer current. If the CRTL expires, the safe state values are placed into the
Reconciled Input Data tag.
Valid Data Being Received
If valid data is being received from the module this output is HI regardless of
whether this data is being moved to the Reconciled Input Data tag. This
output must be HI before you perform a SIL 2 Reset to begin moving actual
data to the Reconciled Input Data tag.
This output goes LO if a valid data packet is not received for a time equaling
three (3) Module RPIs. If this output is toggling LO, verify that the RPI entered
into the Add-On Instruction matches the actual module RPI. The periodic task
rate can also affect this output. If the periodic task rate is too high, then the
packets are not processed often enough. See the 1715 SIL 2 task
recommendations in this manual for configuration recommendations.
Reset Tiedown Fault
If the reset button is HI for longer than 3 seconds, a tiedown fault is declared.
The fault is cleared when the reset button transitions to LO.
CRC Error
CRC Error is HI if the accumulated error count (for detected CRC errors) has
exceeded the allowable threshold.
Duplicate Sequence Number
If the sequence number is a duplicate, data is discarded as invalid and this
output is set HI to indicate the reason.
Low Sequence Number
If the sequence number is lower than expected, data is discarded as invalid
and this output is set HI to indicate the reason.
High Sequence Number
If the sequence number is higher than expected, data is discarded as invalid
and this output is set HI to indicate the reason.
Source IP Error
If any of these check data values, described on
, do not match the
values in the 1715 module configuration, data is declared invalid and
discarded. The appropriate output is set HI to indicate the reason.
Source Slot Error
Destination IP Error
Destination Slot Error
Variant ID Error
Module Connection Status
This output is set LO if the Add-On Instruction detects a connection loss. Input
data is declared invalid and the CRTL is not reset. When the connection is re-
established, this output is set HI.
Add-On Instruction Running
If the 1715 module is at the correct firmware revision level (Variant ID = 2) and
the logic in the Add-On Instruction is being scanned, this output toggles at the
rate of the RPI.
SIL 2 Output Reset Needed
Only for output modules: This output is set HI if a SIL 2 Reset is necessary
reset the outputs from the safe state and begin controlling outputs
programmatically. See
Performing a SIL 2 Reset on page 238
CRTL Countdown
A countdown of the amount of time remaining before the CRTL expires.
Number of Discarded Data
Packets
A count of the data packets that have been discarded as invalid.