LC700 – User’s Guide
3.18
Power –Up Procedure
Breakers
- One breaker to the main CPU.
- One breaker to the backup CPU.
- One breaker to the RIO modules.
Power-up sequence
Power-up sequence refers to the order that each CPU is turned –on. There is a specific breaker
configuration.
1. First, the breaker of the power supply modules of the RIO modules is turned on.
2. Next each the two breakers of each CPU are turned on.
3. Before the CPUs start searching for another CPU, the state of both becomes passive.
4. After powering-up a CPU and if it does not find an active CPU, then, during 2 seconds
interval it will search for another CPU.
5. If it does not find another active CPU it becomes the Active CPU.
I - The algorithm checks which CPU was active in the last power-down. The active CPU in the
last power-down becomes the current active CPU. The CPU passive in the last power-down
becomes the current passive.
II - If both CPUs were passive or active simultaneously in the last power-down, the algorithm
checks the rotary keys to define which CPU will be active. If the rotary key is in the main position (0),
then the CPU is considered active. If the rotary is in the backup position, then the algorithm
considers this CPU as passive.
For further explanation, please check the flowchart in the next page.
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