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Appendix C. Using SDM-CAN on J1939 Networks
Table C-6 Mapping of J1939 Identifier Field Values into a 29-Bit Identifier
Bit
28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
SOF P
3
P
2
P
1
R
1
D
P
P
F
8
P
F
7
P
F
6
P
F
5
P
F
4
P
F
3
P
F
2
P
F
1
P
S
8
P
S
7
P
S
6
P
S
5
P
S
4
P
S
3
P
S
2
P
S
1
S
A
8
S
A
7
S
A
6
S
A
5
S
A
4
S
A
3
S
A
2
S
A
1
Value 0 1 1 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0
This gives a binary value of 01100111100000000001100000000 that can then be
split into three values for use as the ID parameter.
The first value is made up of bits 0..10 which is 01100000000
2
this is converted to
768
10
and used as the first ID parameter.
The second value is made up of bits 11..23 which is 1111000000000
2
this is
converted to 7680
10
and used as the second ID parameter.
The third value is made up of bits 24..28 which is 01100
2
this is converted to 12
10
and used as the third ID parameter.
C.5.2 Finding the Start Bit
The byte number of the Accelerator pedal position value is 2
Table C-7 Accelerator Pedal Position Value Byte Number
1 2 3 4 5 6 7 8
87654321 87654321 87654321 87654321 87654321 87654321 87654321 87654321
The start bit for this value is 49, as it is the least significant bit of the data value
within the data frame that this parameter refers to.
An example for Accelerator pedal position is shown below.
;{CR23X}
;
*Table 1 Program
01: 1.0 Execution Interval (seconds)
;Retrieve Accelerator pedal position Data from CAN network
8: SDM-CAN (P118)
1: 0 SDM Address
2: 4 Time Quanta
3: 5 Tseg1
4: 2 Tseg2
5: 768 ID Bits 0..10 (-- for 11-bit CAN ID)
6: 7680 ID Bits 11..23
7: 12 ID Bits 24..28
8: 2 Rx, unsigned int, LSB 1st
9: 49 Start Bit No.
10: 8 No. of Bits
11: 1 No. of Values
12: 7 Loc [ Throttle ]
C-5