Programming; Twincat Plc; Plc Cycle Time; Fig. 23 Program Running Time - Beckhoff BC9000 Documentation

Programming

6 Programming
6.1

TwinCAT PLC

The Beckhoff TwinCAT Software System turns any compatible PC into a real-time controller with a multi-PLC
system, NC axis control, programming environment and operating station. The TwinCAT programming
environment is also used for programming the BC9000. If you have installed TwinCAT PLC (WinNT4,
Win2000, XP), you can use the Ethernet connection or the serial port for software download and for
debugging.
TwinCAT I/O or TwinCAT PLC can also be used as the Ethernet Master (host), in order to exchange process
data with the Bus Terminal Controller. TwinCAT provides you with the System Manager as a configuration
tool, as well as the drivers and the ADS protocol.
6.2

PLC Cycle Time

The PLC cycle time determines the program's repetition frequency. This time is not deterministic. This
means that the PLC cycle time can become longer in some programs, and can exceed the cycle time that
has been set. If the program requires less time than has been set, it is repeated within the set cycle time,
and the remaining duration is padded with background time.
The processing of the Ethernet and the serial interface runs in the background time. This should be set to
somewhere between 20 and 50 % of the PLC cycle time.
The mean cycle time is measured in order to optimize the system. You will find this in PLC Control under the
Online/Coupler menu item. About 50 % is added to the time determined there, and the result entered as the
PLC cycle time. Set the background time to between 20 and 50 % of the PLC cycle time.
Fig. 23: Program running time
The program running time is composed of the program processing and the K-Bus time. Before the program
is called, the Bus Terminal Controller carries out a K-bus update, and reads the current inputs. Following
the processing of the program, a second K-bus update takes place in order to write the outputs. The
K-Bus time depends on the number and type of Bus Terminals inserted.
The program running time can be shortened by operating only one K-Bus cycle, and this may either be done
before or after program processing. In that case, inputs are read and outputs written in a single K-Bus cycle.
You can make these settings either with the aid of the KS2000 configuration software, or through ADS.
36 Version: 4.0.0 BC9000 and BC9100