Rockwell Automation 1715-OF8I Redundant I/O System User Manual - Manual (Page 224)

224 Rockwell Automation Publication 1715-UM001C-EN-P - March 2014
Chapter 7 Using SIL 2 Add-On Instructions with 1715 Redundant I/O Modules
Table 41 - SIL 2 Add-On Instructions
An additional Add-On Instruction called CRC_calculator is automatically
imported when any of the nine Add-On Instructions listed above are imported.
The CRC_calculator instruction calculates the CRC for incoming packets and
compares the result against the actual CRC received in the packet. The
instruction also calculates the CRC that is placed in the outgoing packet.
SIL 2 check data is added to data packets by the producer and this check data is
verified by the consumer to determine the validity of the data transfer.
For input data from the 1715 modules, the 1715-AENTR adapter is the
producer and the ControlLogix controller is the consumer. The 1715-AENTR
adapter adds the check data, and the Add-On Instructions verify that valid data is
received within the module's connection reaction time limit (CRTL). If valid
data is not received within the CRTL, the instruction substitutes the module's
configured safe state values in place of the invalid data.
For output data to the 1715 modules, the ControlLogix controller is the
producer and the 1715-AENTR adapter is the consumer. The Add-On
Instructions add SIL 2 diagnostic information (check data) to the module
assemblies, including a sequence number, source and destination IDs, and CRC.
The 1715-AENTR adapter verifies that valid data is received within the CRTL.
Outputs are placed into the safe state if the CRTL expires.
The 1715 input modules send data only in one direction, from the
1715-AENTR adapter to the ControlLogix controller. In contrast, for the 1715
output modules, data is sent in both directions (status to the controller and
output data from the controller).
The Add-On Instructions perform error rate monitoring on the input data they
process to verify that the maximum allowed error rate for SIL 2 has not been
exceeded. The error rate monitoring is performed automatically, requires no user
configuration, and will shutdown a link (force Add-On Instruction outputs to
shutdown states and require a SIL 2 Reset) immediately when it is detected.
The Add-On Instructions provide an output (CRC_error) that indicates if this
condition has occured.
Module System Configuration Add-On Instruction Name
1715-IB16D Simplex IB16D_Simplex_SIL2
Duplex IB16D_Duplex_SIL2
1715-OB8DE Simplex OB8DE_Simplex_SIL2
Duplex OB8DE_Duplex_SIL2
1715-IF16 Simplex IF16_Simplex_SIL2
Duplex IF16_Duplex_SIL2
1715-OF8I Simplex OF8I_Simplex_SIL2
Duplex OF8I_Duplex_SIL2
1715-AENTR Duplex AENTR_SIL2