LDU 179.1 Technical Manual rev. 1.10 - February 2019 Page 11 of 45
6 CANopen interface
6.1 General
The CAN interface follows the CAN2.0B recommendations. It receives both - 11 bit identifiers,
and tolerates 29 bit identifiers. It only transmits 11 bit identifiers.
The
CAN rate
is setup as default to
500 kbit/s
.
The LDU is always quiet on the CAN bus until the NMT Start command is received, except for
the very first ‘node guard’ message.
When started by the NMT Start the LDU 179.1 starts transmitting TPDO1 messages with weight and status.
The default is the net 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 checkweigher 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 re-triggers.
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.
RPDO3 and RPDO4 are ignored by the LDU.
SDOs are handled according to profile and CANopen recommendation.
The LDU supports both
‘node guarding’ and ‘heart beat’.
