Detroit Diesel DDEC VI Application And Installation page 380

COMMUNICATION PROTOCOLS
6.2 SAE J1587 DATA LINK
SAE RP J1587 defines the recommended format of messages and data being communicated
between microprocessors used in heavy-duty vehicle applications. SAE J1587 Data Link +
and SAE J1587 Data Link - as shown on the Vehicle Interface Harness schematic are used as
the J1587 communication link. These circuits also exist in the nine-pin Diagnostic Connector,
Cab for use with the diagnostic tools.
NOTE:
The maximum length for the SAE J1587 Data Link is 40 m (130 ft).
6.2.1 MESSAGE FORMAT
A complete description of the CPC parameters is provided within this section of the manual.
CPC transmits parametric data at SAE J1587 recommended rates in packed message form. The
first byte or character of each message is the Message Identification character (MID). The MID
identifies which microcomputer on the serial communication link originated the information.
Each device in the system originating messages must have a unique MID. The assignment of
MIDs should be based on those listed in SAE RP J1587. The primary MID is 128.
The ProDriver display uses MID 171. Off-board diagnostic tools like hand-held readers should
be identified by MID 172. Off-board programming stations like Vehicle Engine Programming
Station (VEPS) should be identified by MID 182. Messages using MIDs as recommended by
SAE RP J1587 will be responded to by the CPC.
Subsystems also require identifiers. The subsystem identifier character (SID) is a single byte
character used to identify field-repairable or replaceable subsystems for which failures can be
detected or isolated. SIDs are used in conjunction with SAE standard Diagnostic Trouble Codes
defined in J1587 within PID 194.
The identifiers used by CPC are defined and listed in Table 6-1.
Identifier
Failure Mode Identifier (FMI)
Message Identification Character (MID)
Parameter Identification Character (PID)
Subsystem Identification Character (SID)
Table 6-1 Identifiers Used by CPC
6-4
Description
The FMI describes the type of failure detected in the
subsystem and identified by the PID or SID.
The MID is the first byte or character of each
message that identifies which microcomputer on
CPC SAE J1587 DL serial communication link
originated the information.
A PID is a single byte character used in CPC SAE
J1587 DL messages to identify the data byte(s) that
follow. PIDs identify the parameters transmitted.
A SID is a single byte character used to identify
field-repairable or replaceable subsystems for which
failures can be detected or isolated.
All information subject to change without notice. (Rev. 01/07)
7SA827 0701 Copyright © 2007 DETROIT DIESEL CORPORATION