Precautions for Modifying an SFC Section Online
| WARNING | |
|---|---|
RISK OF UNINTENDED OPERATION Transfer the application from primary controller to the
standby controller 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 controller tests the SFC_MISMATCH bit. The SFC_MISMATCH bit is set
when the structure of at least one SFC section
in the primary controller differs from that
section in the standby controller. If this
bit is set, the controller 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 controller
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 controller. |
4 |
Transfer the application from the
primary controller to the standby controller. 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:
|