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:
Schematic: CANopen default identifier

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 hex / dec

Object for communication Parameter / mapping

NMT

Boot-Up

0

0x00 / 0

- / -

SYNC

Synchronization

1

0x80 / 128

0x1005 + 0x1006 / -

Peer-to-peer objects

Object

Function with I/O devices

Function code

Resulting COB ID hex / dec

Object for communication Parameter / mapping

Emergency

Status / error

1

0x81 - 0xFF/ 129 - 255

- / -

PDO1 (tx)

dig. inputs

11

0x181 - 0x1FF / 385 - 511

0x1800 / 0x1A00

PDO1 (rx)

digital outputs

100

0x201 - 0x27F/ 513-639

0x1400 / 0x1600

PDO2 (tx)

analog inputs

101

0x281 - 0x2FF/ 641-767

0x1801 / 0x1A01

PDO2 (rx)

analog outputs

110

0x301 - 0x37F/ 769-895

0x1401 / 0x1601

PDO3 (tx)

analog inputs*

111 

0x381 - 0x3FF / 897 - 1023

0x1802 / 0x1A02

PDO3 (rx)

analog outputs*

1000 

0x401 - 0x47F/ 1025 - 1151

0x1402 / 0x1602

PDO4 (tx)

analog inputs*

1001 

0x481 - 0x4FF/ 1153 - 1279

0x1803 / 0x1A03

PDO4 (rx)

analog outputs*

1010

0x501 - 0x57F/ 1281 - 1407

0x1403 / 0x1603

SDO (tx)

Parameter

1011

0x581 - 0x5FF/ 1409-1535

- / -

SDO (rx)

Parameter

1100

0x601 - 0x67F/ 1537-1663

- / -

Guarding

Life and node guarding,
heartbeat,
boot-up message

1110

0x701 - 0x77F/ 1793-1919

(0x100C, 0x100D, 0x100E, 0x1016, 0x1017)

* For historical reasons, the Beckhoff default mapping applies to PDOs 3 and 4 in Beckhoff I/O devices. 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 Bus Coupler documentation.

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.