Product Manual CANcockpit
TU00-0726-5111102 Technische Änderungen vorbehalten 0609 Technical details subject to change 5.2 - 4
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CANopen-Specification for CANcockpit
5.2.3 Hardware Requirements
CANopen Baud Rates and Sample Points for CANcockpit
Standard CAN Bus Baud Rates on the CDVV controller at 10MHz crystal frequency
Standard
Baud Rate
Baudrate
Prescaler
Time
Quantum
Bit
Time
Nominal Bit
Time
Sample
Point
Comment
BPR tQ
[kHz] [usec] [tQ] usec [tQ]
1000 0 0.100 10 1 8
some restrictions due to message
processing
500 0 0.100 20 2 17 as above
250 1 0.200 20 4 17 SAE J1939
125 2 0.400 20 8 17
50 9 1.000 20 20 17
20 24 2.500 20 50 17
10 49 5.000 20 100 17
The 800 kHz baud rate is not possible, because the bit time is 1.25usec, whereas the time quantum at 10MHz is 0.1usec.
Galvanic isolation
There is no galvanic isolation required for CANopen. However it is recommended to apply it, if the bus length exceeds 200m.
11bit Identifiers
CANopen is based on 11bit Ids. 29bit Ids cannot be used together with 11bit Ids.
5.2.4 Firmware Requirements
CAN Interfaces
CAN I to be selectable for CANopen or J1939 (both with full functionality)
CAN II to be selectable for J1939 (full functionality) or CANopen (only additional PDO in)
Master or Slave?
In a CANopen network there is only one NMT-master, which controls all devices on the bus. The master is able to set the
operational state of the connected slave devices.
CANcockpit acts as a slave on the CANopen network.
However it is desirable that CANcockpit would also have minimum CANopen NMT-Master capabilities in case there is no
other CANopen Master. An example for this situation is a system with 4 Slave-Sensor-Devices connected to the CANopen
interface of the CANcockpit Main-Gauge.
In a small system without NMT-master CANcockpit can be configured to move automatically from pre-operational to
operational state. This allows it to send and receive PDOs without an NMT-master. The IDs for the RPDOs and TPDOs can
also be configured via EEPROM settings to match the requirements of the application.
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