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Overview
CAN Data Frame
ARBITRATION FIELD
START OF
COMM.
FRAME
OBJECT ID
(COB ID)
1 BIT
11 OR 29 BITS
FUNCTION CODE
10
9
Communication
Object
NMT
SYNC
TIME STAMP
EMERGENCY
PDO 1 (Tx)
PDO 1 (Rx)
PDO 2 (Tx)
PDO 2 (Rx)
PDO 3 (Tx)
PDO 3 (Rx)
PDO 4 (Tx)
PDO 4 (Rx)
SDO (Tx)
SDO (Rx)
NODEGUARD
NCAN-02 Installation and Start-up Guide
This chapter describes the communication on a CANopen network.
CAN employs data frames for transferring data between the host
(controller) and the nodes on the bus. The following figure presents the
structure of the data frame.
REMOTE
CONTROL
TRANS-
FIELD
MISSION
REQUEST
1 BIT
6 BITS
8
7
6
5
Function Code
(Binary)
0000
0001
0010
0001
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1110
Inside the CANopen data frame, different types of Communication
Objects are used to convey the data. Process Data Objects (PDO) are
used for transmitting time-critical process data (references, control
commands, status information); Service Data Objects (SDO) are used
for less time-critical data, e.g. parameters. In addition, there are Special
Function Objects and Network Management Objects.
Chapter 6 – Communication
CYCLICAL
DATA
REDUNDANCY
FIELD
0 TO 8 BYTES
NODE ID
4
3
2
1
COB ID
COB ID
(Hex)
(Dec)
0×00
0
0×80
128
0×100
256
0×81 ... 0×FF
129 ... 255
0×181 ... 0×1FF
385 ... 511
0×201 ... 0×27F
513 ... 639
0×281 ... 0×2FF
641 ... 767
0×301 ... 0×37F
769 ... 895
0×381 ... 0×3FF
897 ... 1023
0×401 ... 0×47F
1025 ... 1151
0×481 ... 0×4FF
1153 ... 1279
0×501 ... 0×57F
1281 ... 1407
0×581 ... 0×5FF
1409 ... 1535
0×601 ... 0×67F
1537 ... 1663
0×701 ... 0×77F
1793 ... 1919
ACKNOWL-
EDGE
CHECK
FIELD
16 BITS
2 BITS
0
END OF
FRAME
7 BITS
6-1
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