Data Exchange PC/Bus Terminal Controller
For Bus Terminal controllers you can define below PLC variables data exchange variables (see example in the tree view below) for the fieldbus-based PC to PC communication.
If you select a BC in the tree view of the TwinCAT System Manager, the following BC Mini PLC dialogue (amongst others) will appear on the right-hand side:
”PLC” Dialogue
PLC Cycle Time
The reserved Mini PLC cycle time. During this period, no data will be sent by the BC to the fieldbus.
Background Time
Time for the processing of the communication via the fieldbus (includes program download, debugging,..).
PLC Var. Offs IN
Start offset of the data exchange variables in the input area of the BC Process Image.
PLC Var. Offs OUT
Start offset of the data exchange variables in the output area of the BC Process Image.
AMS Response during download
Can be disabled for compatibility reasons in old Bus Terminal controllers (BC3100 and BC2000). Newer bus controller firmware versions acknowledge the receipt of individual download sequences. This checkbox must therefore be activated (in all cases for BC9000).
Start with Configuration Error
Even if the configured BC9000 is not connected to the network, it is possible to start the TwinCAT system if this checkbox is enabled.
Retain Data
Store Retain Data: Activates the support of residual data in the Bus Terminal controller.
Size: Size of the retain data area within the Bus Terminal controller (%Mx0 .. %Mxy).
KBus Update
Double Cycle: Activates the execution of BC station I/O cycles (KBus Update) within before and after each PLC cycle.
Before PLC: A KBus update will be carried out before executing the PLC cycle.
After PLC: A KBus update will be carried out after executing the PLC cycle.
Firmware Update (via COMx)
This function is used to update a BC firmware version.
”Variable” Dialogue
After selecting Adding Variables you will see the dialogue for the selected variable on the right-hand side under the tree input PLC Variables, as described in the Variables Information rubric.
You should, of course, use intelligent names for the data exchange variables as these are used when Exporting Variable Information as variable names in the local BC Process Image.
You may now Link the data exchange variables with existing tasks.
Sample BC configuration
The image below shows both data exchange variables and fieldbus variables. The BC manages terminals 4 - 9 locally.
