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RTU32M Series User Guide
Brodersen A/S, Islevdalvej 187, DK-2610 Roedovre, Denmark, Tel: +45 45 35 26 27, Fax: +45 45 35 26 29, Email: [email protected]
August 2018
50
8
RTU32M cycle / scan time
All tasks run independent of each other. The two I/O cycles are running as fast as possible to ensure that the basic RTU32M I/O
database reflects the physical I/Os
–
both internal I/O and I/O on the expansion modules. The PLC runtime program cycle time depends
on the size of the application program, and can vary from less than 1 msec to >100 msec. At runtime application start, all inputs are
read from the I/O database and at the end of each cycle the outputs are written to the I/O database.
8.1
RTU scan time
The RTU scan time can be set to 0 (zero) which automatically assigns some time for operating system household activities between
each runtime
program cycle. In this case the program runs as “fast” as possible. The automatic assignment of household execution time
ensures all necessary operating system processes can be maintained with a good margin.
If you set the PLC scan time to a fixed value, you can in some cases obtain a better general scan time for your application program. But
it is IMPORTANT to realise that you are then responsible to leave time for household operations.
IMPORTANT NOTICE: If you leave too short time for household operations, the firmware will automatically ensure that your PLC
program does NOT compromise necessary household time. It also means that you will get a slower scan cycle time than adjusted. If
your RTU/PLC application includes many TCTP/IP based connections over LAN connections, it is recommended to fix the scan time to
a value leaving more time to the OS household than automatically assigned.
8.2
LB2 Bus and Internal I/O Bus scan time
The scan time of the RTU32M internal I/O is running as fast as possible (in micro seconds).
(t) PLC
Program cycles
PLC scan time
PLC cycle
Household time