Flintec MCS-64 CANbus - Manual (Page 8)

Page Manual MSC-64 8
2.3 CANopen
The CANopen Gateway follows the CAN2.0B recommendations. It receives both 11-bit
identifiers, and tolerates 29-bit identifiers. It only transmits 11-bit identifiers.
The Gateway is always quiet on the CANbus until the NMT Start command is received,
except for the very first ‘node guard’ message.
When started, the TPDO1 is used to send current status information. The backplane is
scanned approx. 10 times per second. This gives 64 modules X 10 = 640 status messages
per second if all 64 modules are installed. The TPDO1 holds the Gateway status, the module
number, the module status and either net or gross weight, depending on the SDO selection.
The default is the Gross value. When filling is in progress the Gateway transmits a TPDO2
every time a module changes state to ‘wait for trigger’. This TDPO2 contains the module
number, the module status and the dosed weight. In Check Weigher applications the
TPDO2 is used to send triggered measurements.
With RDPO1 frames you can send simple commands without an acknowledgement. The
functions are: select Gross or Net value in TPDO1, Set or Clear System zero, Set or Clear
Tare.
With RPDO2 frames you can send Triggers or Stop triggers. For the filling application the
trigger can be used to start the Filling Cycle. On checkweigher applications the trigger can
start measurements and a stop-trigger will stop further internal retriggers.
In case of an overrun, error or failure an EMERGENCY message is sent to the CAN
controller indicating the nature of the error or failure.
EMERGENCY messages are transmitted when the CAN controller tries to set up a module
not present, or not functioning, or when a module fails to answer the normal backplane scan
or when a module comes back on-line.
RPDO3 and RPDO4 are ignored by the Gateway.
SDOs are handled according to profile and CANopen recommendation.
The NMT protocol will use the ‘node guarding’ method (no heartbeat), but are otherwise fully
implemented
The “SDO Block Download Protocol” may be implemented later.