Identifier Allocation

Default identifier

CANopen provides default identifiers for the most important communication objects, and these are derived from the 7-bit node address (the node ID) and a 4-bit function code in accordance with the following scheme:

Identifier Allocation 1:

For broadcast objects the node ID is set to 0. This gives rise to the following default identifiers:

Broadcast objects

Object

Function

Function code

Resulting COB ID

Object for communication Parameter / mapping

hex

dec

NMT

Boot-Up

0

0x00

0

- / -

SYNC

Synchronization

1

0x80

128

0x1005

Peer-to-peer objects

Object

Function

Function code

Resulting COB ID

Object for communication Parameter / mapping

hex

dec

Emergency

Status / error

1

0x81 - 0xFF

129 - 255

- / -

PDO1 (tx)

dig. inputs

11

0x181 - 0x1FF

385 - 511

0x1800

PDO1 (rx)

digital outputs

100

0x201 - 0x27F

513 - 639

0x1400

PDO2 (tx)

analog inputs

101

0x281 - 0x2FF

641 - 767

0x1801

PDO2 (rx)

analog outputs

110

0x301 - 0x37F

769 - 895

0x1401

PDO3 (tx)

analog inputs*

111 

0x381 - 0x3FF

897 - 1023

0x1802

PDO3 (rx)

analog outputs*

1000 

0x401 - 0x47F

1025 - 1151

0x1402

PDO4 (tx)

analog inputs*

1001 

0x481 - 0x4FF

1153 - 1279

0x1803

PDO4 (rx)

analog outputs*

1010

0x501 - 0x57F

1281 - 1407

0x1403

SDO (tx)

Parameters

1011

0x581 - 0x5FF

1409 - 1535

- / -

SDO (rx)

Parameters

1100

0x601 - 0x67F

1537 - 1663

- / -

Guarding

Life/node guarding,
Heartbeat,
Boot-up message

1110

0x701 - 0x77F

1793 - 1919

(0x100C

*) The Beckhoff Default Mapping applies to PDO 3 + 4. In most configurations, PDOs 3 and 4 contain data related to analog inputs and outputs, but there can also be "excess" data from digital I/Os, or data from special terminals. Details may be found in the section covering PDO Mapping.

Up until version 3 of the CANopen specification, default identifiers were assigned to 2 PDOs at a time. The BECKHOFF Bus Couplers up to firmware status BA correspond to this issue of the specification. After firmware status C0 (CANopen version 4), default identifiers are provided for up to 4 PDOs.

Manufacture-Specific Default Identifiers for Additional PDOs

Default Identifiers for Additional PDOs

Identifiers are not assigned to the additional PDOs that are filled by the Beckhoff Bus Couplers in accordance with the standard scheme. The user must enter an identifier for these PDOs in the object directory. It is easier to activate the occupied PDOs by means of object 0x5500.

This entry in the object directory extends the default identifier allocation up to 11 PDOs. This creates the following identifiers:

Object

Function code

Resulting COB ID (hex)

Resulting COB ID (dec)

PDO5 (tx)

1101

0x681 - 0x6BF

1665 - 1727

PDO5 (rx)

1111

0x781 - 0x7BF

1921- 1983

PDO6 (tx)

111

0x1C1 - 0x1FF

449 - 511

PDO6 (rx)

1001

0x241 - 0x27F

577 - 639

PDO7 (tx)

1011

0x2C1 - 0x2FF

705 - 767

PDO7 (rx)

1101

0x341 - 0x37F

833 - 895

PDO8 (tx)

1111

0x3C1- 0x3FF

961 - 1023

PDO8 (rx)

10001

0x441 - 0x47F

1089 - 1151

PDO9 (tx)

10011

0x4C1 - 0x4FF

1217 - 1279

PDO9 (rx)

10101

0x541 - 0x57F

1345 - 1407

PDO10 (tx)

10111

0x5C1 - 0x5FF

1473 - 1535

PDO10 (rx)

11001

0x641 - 0x67F

1601- 1663

PDO11 (tx)

11011

0x6C1 - 0x6FF

1729 - 1791

PDO11 (rx)

11101

0x741 - 0x77F

1857 - 1919

Note
Warning

Index 0x5500 must not be used if Bus Couplers with more than 5 PDOs are present in networks with node numbers greater than 64, otherwise identifier overlaps can occur.