DDEC VI ELECTRONIC CONTROLS APPLICATION AND INSTALLATION
6.2.2
SAE J1708/J1587 MESSAGE PRIORITY
Each messagesent by CPC is assigned a priority on a scale of 1 to 8, in compliance with the
message priority assignment speci
fi
ed in SAE RP J1708. The most critical message has a priority
of one. The message assignments are listed in Table 6-2. All devices transmitting messages across
DDEC's SAE J1708/J1587 Data Link must be prioritized and transmitted in this manner.
Priority
Description
1 and 2
Reserved for messages that require immediate access to the bus.
3 and 4
Reserved for messages that require prompt access to the bus in order
to prevent severe mechanical damage.
5 and 6
Reserved for messages that directly affect the economical or ef
fi
cient
operation of the vehicle.
7 and 8
All other messages not
fi
tting into the previous priority categories.
Table 6-2
Message Priority Assignments
6.2.3
SAE J1587 PIDS REQUIRING ACTION
CPC will respond to data requests per the J1587 PID requests shown in the next sections.
Data Request
The format for a data request is shown below.
PID
Data
0
a
a - Parameter number of the requested parameter
Component Speci
fi
c Request
The format for a component speci
fi
c request is shown below.
PID
Data
128
a b
a - Parameter number of the requested parameter
b - MID of the component from which the parameter data is requested
NOTE:
CPC responds with the appropriate data provided the MID in byte (b) matches the MID
stored in calibration. The primary MID for CPC is 128.
All information subject to change without notice.
(Rev. 01/07)
6-5
7SA827 0701
Copyright © 2007 DETROIT DIESEL CORPORATION
