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 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 . 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 NOTE: Alternatively, you can automate the
transfer in program logic using a code sequence like the following:
|