Modifying an SFC Section Online
Original instructions
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Precautions for Modifying an SFC Section Online
WARNING
RISK OF UNINTENDED OPERATION
Transfer the application from primary PAC to the standby PAC after each online modification of a MAST task section that is programmed using the sequential function chart (SFC) programming language.
Do not execute a switchover or trigger a swap before this transfer is successfully completed.
Failure to follow these instructions can result in death, serious injury, or equipment damage.
When the M580 Hot Standby system executes a switchover or a swap, the new primary CPU tests the SFC_MISMATCH bit. The SFC_MISMATCH bit is set when the structure of at least one SFC section in the primary PAC differs from that section in the standby PAC. If this bit is set, the CPU re-initializes the state-machine of all the modified SFC sections to help prevent any unpredictable behavior of the user application.
To avoid the re-initialization of the SFC state-machines when you modify an SFC section, follow these steps:
Step
Action
1
Confirm that the LOGIC_MISMATCH_ALLOWED bit is set to 1.
NOTE: If logic mismatch is not allowed, the standby PAC enters wait after step 3.
2
Make the online edit to the SFC section in Control Expert.
3
Build the online change in Control Expert by selecting Build → Build Changes.
The modification is made to the program running in the primary PAC.
4
Transfer the application from the primary PAC to the standby PAC. Use a Control Expert animation table to set the CMD_BACKUP_APPLI_TRANSFER bit to 1.
NOTE: Alternatively, you can automate the transfer in program logic using a code sequence like the following:
if (ECPU_HSBY_1-->SFC_MISMATCH = 1)
then ECPU_HSBY_1-->CMD_BACKUP_APPLI_TRANSFER = 1