Group Extension (GE)
The Group Extension field provides 4,069 parameter groups per page.
Source Address (SA)
There should only be one device on the network with a given source address. The
Source Address field therefore ensures the CAN identifier is unique, as required by CAN.
Data field
The J1939 protocol data unit (PDU) can contain up to 8 bytes, as per the definition of
the CAN data frame.
5.2
Parameter group number
The PGN uniquely identifies the parameter group (PG) that is being transmitted in the
message. Every PG (grouping of specific parameters) has its own specific definition
comprising the assignment of each parameter within an 8-byte data field (size in bytes,
location of the LSB), and the transmission rate and priority of the message.
3 Bit
Priority
1 Bit
Reserved
1 Bit
Data Page
8 Bit
PDU Format
8 Bit
PDU Specific
8 Bit
Source
Adress
1 Bit
Reserved
1 Bit
Data Page
8 Bit
PDU Format
8 Bit
PDU Specific
29 Bit
CAN ID
Figure 3: Parameter group number
Generally speaking, a distinction can be made between messages that are exchanged
between two nodes by direct addressing (PDU format 1), and broadcast messages that
are send to all nodes on the bus (PDU format 2).
The PDU format values 00h to EFh are reserved for point-to-point messages; the PGN
also contains the destination address. Broadcast messages are sent with PDU format
values from F0h to FFh. The Group Extension field increases the number of available
broadcast messages. The encoder uses broadcast messages with PDU format 2 to
send the process data. Direct addressing in PDU format 1 using the Proprietary A PGN
is supported for configuration.
5.3
Device name and address
With the factory settings, the encoder starts with the address 224d (E0h). Dynamic
address allocation is supported. At startup the encoder sends a suitable address claim
telegram with the address used. This message contains the 64-bit device name by
means of which the sensor can be uniquely identified. The priority on the bus is also
determined based on the name.
The 64-bit device name contains the following fields:
SAE J1939 INTERFACE
5
8027379/2022-01-21 | SICK
O P E R A T I N G I N S T R U C T I O N S | AHS/AHM36 SAE J1939
AHS/AHM36 SAE J1939 Inox
15
Subject to change without notice
