SMAR LC700 - Power -Up Procedure; Communication with Remote I;O Modules

LC700 – User’s Guide
3.34
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.
Communication with Remote I/O Modules
The remote I/O modules (RIO) are scanned only if the name of the configuration and data are the
same in the main CPU and RIO CPU. The passive CPU sends polling commands to check
periodically whether it is necessary to assume control.
As seen in the system architecture picture, the RIO modules are connected to the system through
two different and redundant channels.
There are two ports to be considered:
- RIO Active Port: Port being scanned by the active CPU, i.e., through this port the MODBUS
variables are read and written.
- RIO Passive Port: In this port the passive CPU checks the conditions of the active and passive
ports.
Switch over procedure
During the normal functioning of the system, there’s a switching procedure. It is based on the
number of the RIO CPUs that the active CPU can communicate with (NRIOactive) and the number
of RIO CPUs that the passive CPU can communicate with (NRIOpassive).
If NRIOactive is shorter than NRIOpassive, then there is a switching over procedure that makes the
current active CPU the passive CPU and the old passive CPU the current active CPU. This
procedure ensures that the system reads the biggest amount of I/O MODBUS variables.
LEDs for Status Indication
- A solid RUN LED (green, on or off) indicates if the CPU is in Active state while a blink RUN LED
indicates that the CPU is in Passive state.
- A solid HOLD LED (yellow, on or off) indicates if the CPU has been configured properly, while a
blink HOLD LED indicates that it was not.
- A solid FORCE LED (red, on or off) indicates if the CPU is in FORCE-IN, FORCE-OUT or
SAFE-OUT mode, or not.
- FORCE LED indicator on Passive CPU is blinking. It indicates that the hardware settings is not
correct (rotary switch BR for RIO or firmware version).