How to Program a Quantum Hot Standby Application
Original instructions
Processor Configuration
There are two types of MAST task execution modes:
When the periodic mode is used, the user-defined period must take into account the longer mast task periods necessary in a redundant system.
The following table presents the characteristics of MAST tasks that may be adjusted by the user in Control Expert:
Characteristics
Control Expert Default Values
Max period (ms)
255
Default period (ms)
20 (Note: Set to 80 ms as an initial value for Hot Standby systems)
Min. period (ms)
1 (0 if the Cyclic MAST task execution mode is selected)
Period increment (ms)
1
Max Watchdog (ms)
1500
Default Watchdog (ms)
250
Min. Watchdog (ms)
10
For more details, see Adjusting Mast Task Properties.
Detecting Cold and Warm Starts of a Quantum Hot Standby PLC
In a Quantum Hot Standby PLC, only the System Word %SW10 and the System Bit %S1 can be used to detect respectively a Cold Start and a Warm Start.
To process your application based on the type of start, the program must test whether %SW10.0 is reset to 0 (or %S1 is set to 1) at the start of first MAST task. %SW10 and %S1 can be tested by the application in either the Primary or Standby mode.