8: J1939 C
OMMUNICATION
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ANUAL
FC9Y-B1730
Device Address
Addresses are defined between 0 and 255.
However, 254 (null address) is the result of an address conflict and is only used when an address cannot be obtained. 255 (global
address) is used when broadcasting messages to all CAs without specifying a specific CA.
NAME (64 bits total)
The 64-bit NAME is split into multiple fields. The content for a portion of the fields is already defined in the standard. NAME must
be set to a value that is not duplicated by another device on the same J1939 communication network. For details on the definition
of each bit, refer to the SAE J1939 standard.
*1 "Yes" items are defined in the standard. Set those items according to the used network and purpose.
The CAN J1939 All-in-One Type resolves address conflicts with CAs according to the value of the Arbitrary Address Capable bit.
If the Arbitrary Address Capable bit is 0
The CAN J1939 All-in-One Type operates as a fixed address CA. If there is a CA that has the same address as the local address,
the CAN J1939 All-in-One Type can exchange messages with the set local address if its priority is high.
If the CAN J1939 All-in-One Type priority is low, the local address is 254 (null address).
If the Arbitrary Address Capable bit is 1
The CAN J1939 All-in-One Type operates as a dynamic address CA. If there are CAs that duplicate the local address, the local
address is compared to that of the corresponding CA, and if the CAN J1939 All-in-One Type priority is lower, it repeatedly
attempts to acquire another address. When the local address has been determined, messages can be exchanged.
If the local address was not determined by the last address, it is set to 254 (null address).
PGN
CAs exchange parameter information such as the engine RPM and the on/off status of switches. These parameters are defined in
advance and assigned unique ID numbers (SPNs). The parameters are also grouped according to content, and these parameter
groups are assigned unique ID numbers (PGN).
CAs exchange messages for each PGN.
Example: SPNs that make up PGN 1792 General Purpose Valve Pressure
*1
Address Description Details
0 to 253 Address range allocated to CAs
For a portion of addresses, the use has been determined according to the type of
connected device. For details, refer to the SAE J1939 standard.
254 Null address
Set as the result of an address conflict when an address between 0 and 253 could not be
obtained.
255 Global address Used when transmitting a message as a broadcast.
Field Name Bit Length SAE Defined
*1
Item
Arbitrary Address Capable 1 (high order) — Dynamic address support
Industry Group 3 Yes Industry group
Vehicle System Instance 4 — Vehicle system instance
Vehicle System 7 Yes Vehicle system
Reserved 1 Yes Reserved (fixed as 0)
Function 8 Yes Function
Function Instance 5 — Function instance
ECU Instance 3 — ECU instance
Manufacturer Code 11 Yes Manufacturer code
Identify Number 21 (low order) — ID number
SPN Parameter Name Data Size
4086 Valve Load Sense Pressure 2 bytes
4087 Valve Pilot Pressure 1 byte
4088 Valve Assembly Load sense Pressure 2 bytes
4089 Valve Assembly Supply Pressure 2 bytes
*1 From J1939-71
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