Offline Application Modification with Allowed Application Mismatch
Original instructions
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Procedure
WARNING
UNEXPECTED EQUIPMENT BEHAVIOR
Before transferring a modified application to the Standby CPU:
  • Examine carefully all the impacts of the modifications on the application.
  • Check that the modified application does not have adverse effects on the process.
Failure to follow these instructions can result in death, serious injury, or equipment damage.
To make offline modifications to an application program in either CPU, follow these steps:
Step
Action
1
Verify the following:
  • The HSBY_BUILD_OFFLINE function block is implemented in the application program in both Primary and Standby CPU.
  • Application program is equal in Primary and Standby CPU.
  • The Standby On Logic Mismatch parameter is set in the Hot Standby configuration tab.
2
Connect Control Expert to the Primary CPU.
3
Set to 1 the ALLOW_MISMATCH bit of the HSBY_BUILD_OFFLINE function block.
This setting authorizes the CPU to remain synchronized with its pair if a program is modified offline.
NOTE: Verify that the section where the function block resides is executed by the Primary and the Standby CPU (verify the CPU section execution settings in the Hot Standby tab).
4
Confirm that the logic mismatch is enabled.
5
Disconnect Control Expert from the CPU.
6
Modify the application program offline.
NOTE: Only modifications within the scope of the application code and/or some items under the DTM browser modifications are working as valid offline build modification for the Standby CPU. Any other modifications (configuration changes for example) are not taken into account by the HSBY_BUILD_OFFLINE function block.
7
Perform a Build Changes and save.
NOTE: Do not perform a Rebuild All Project because the Standby CPU may not switch to the RUN STANDBY state after the program download and RUN. The swap from Standby to Primary cannot be performed.
8
Connect Control Expert to the Standby CPU.
9
Open the modified application program.
10
Download the program in the Standby CPU.
11
Select RUN.
NOTE: Check that the CPU is now in WAIT state.
NOTE: If the CPU does not transition to WAIT state, proceed as indicated in the following Workaround topic.
12
For safety Hot Standby CPUs, check if the safe part of the new application has been modified (SAFETY_LOGIC_MISMATCH bit = 1). If so, set the operating mode of the standby PAC to maintenance mode.
13
On the Standby CPU set to 1 the ALLOW_MISMATCH bit of the HSBY_BUILD_OFFLINE function block.
This setting authorizes the CPU to remain synchronized with its pair if a program is modified offline.
Result: The Standby CPU switches from WAIT to RUN STANDBY state.
NOTE: Verify that the section where the function block resides is executed by the Standby CPU (verify the CPU section execution settings in the Hot Standby tab).
14
Verify that:
  • The Primary CPU is in RUN PRIMARY.
  • The Standby CPU is in RUN STANDBY.
15
Perform a switchover using the CMD_SWAP command, or by clicking Animation → Task → Swap controllers → Primary <-> Standby in the CPU configuration window in Control Expert.
NOTE: Verify that the Standby CPU switched to Primary CPU.
16
Perform an application transfer to the Standby CPU.
17
Perform an application RUN to the Standby CPU.
18
On the Standby and Primary CPU reset to 0 the ALLOW_MISMATCH bit of the HSBY_BUILD_OFFLINE function block.
NOTE: Application mismatch topic is discussed in the configuration compatibility section.
Workaround When the Standby CPU Does Not Transition to WAIT State
If the Standby CPU does not transition to WAIT state after the RUN command in step 11 (a Rebuild All Project has been performed for example), the initial program and configuration need to be transferred in the Standby CPU.
Step
Action
1
Connect Control Expert to the Primary CPU
2
Upload the application program from the Primary CPU for future offline modifications.
NOTE: The modifications done previously to the application program in Control Expert are lost.
3
Perform an application transfer to the Standby CPU.
4
Perform an application RUN to the Standby CPU.
5
Disconnect Control Expert from the CPU.
6
Modify the application program and repeat the Procedure actions from step 6.
Use Case
In an existing Hot Standby system, the process to modify an application offline and transfer it to the Primary and Standby CPU follows these macro steps (refer to the preceding detailed procedure for more information):