Flintec MCS-64 CANbus - Manual (Page 7)

Manual MCS-64 Page 7
2 System Detailed Design
2.1 General
This software connects a CANopen network to the local backplane modules. The Gateway
transports commands and responses to and from the CANbus. It scans the LDM modules for
their status and then transmits this status information continuously to the CAN controller.
CANopen
ADAPTOR
CANopen
ADAPTOR
BACKPLANE
LDM and other IO
Up to 64 modules per backplane
CAN controller
CAN BUS
Figure 1- CANopen Gateway in context
2.2 Backplane handling
The Gateway must continuously scan the backplane modules. It keeps track of which
modules are present and those that are not. The Gateway communicates with 4 levels of
priority on the backplane.
The highest priority communication is initiated on direct commands from the CAN controller
either by accessing a SDO or by using RPDO3.
The second highest priority is given to LDM modules in the final filling stage. The Gateway
reports the end of filling for each module with a TPDO2 containing the module number,
module status, and for example the dosed weight.
The third priority is the normal module scan. The Gateway continuously transmits TPDO1
with the status information for each module.
At a very low priority the Gateway looks for backplane modules that aren’t recorded as
active, in order to re-establish communication with modules that may have been restarted to
recover from failure.
The Gateway always informs the CAN controller when a module fails, or comes back online.