58 of 76ELM327DSH Elm Electronics – Circuits for the Hobbyist
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Programmable Parameter Summary (continued)
PP Description Values Default Type
2C
2D
2E 80
(10000000)
2F 0A
(50 Kbps)
Protocol B (USER1) baud rate divisor. See PP 2B for a description.
00 to FF
E0
(11100000)
04
(125 Kbps)
01 to 40
00 to FF
Protocol C (USER2) CAN options. See PP 2C for a description.
Protocol C (USER2) baud rate divisor. See PP 2B for a description.
01 to 40
R
Protocol B (USER1) CAN options.
Each bit of this byte controls an option, as follows:
b7: Transmit ID Length 0: 29 bit ID 1: 11 bit ID
b6: Data Length 0: fixed 8 byte 1: variable DLC
b5: Receive ID Length 0: as set by b7 1: both 11 and 29 bit
b4: baud rate multiplier 0: x1 1: x 8/7
(see note 3)
b3: reserved for future - leave set at 0.
b2, b1, and b0 determine the data formatting options:
b2 b1 b0 Data Format
0 0 0 none
0 0 1 ISO 15765-4
0 1 0 SAE J1939
Other combinations are reserved for future updates – results will
be unpredictable if you should select one of them.
R
R
R
2B 02
(250 Kbps)
01 to 40Protocol A (SAE J1939) CAN baud rate divisor.
The protocol A CAN baud rate is determined by this value
rate (in kbps) = 500 ÷ value
For example, setting this PP to 19 (ie. decimal 25) provides
a baud rate of 500/25 = 20 kbps.
R
Notes:
1. The ELM327 does not accept decimal digits for the Programmable Parameters - all values are hexadecimal.
2. Several Programmable Parameters describe options in terms of bits. For all of them, b7 is the msb, and b0
is the lsb. As an example, the PP 2C default value of E0 can be shown as 11100000 in binary. This number
has has b7, b6 and b5 set to 1’s, while b4 to b0 are all 0’s.
3. When b4 of PP 2C or PP 2E are set, the CAN baud rate will be increased by a factor of 8/7, but the baud
rate displayed by the AT DP command will still show the base rate (as set by PP 2D or PP 2F). For example,
if you set PP 2C b4 to 1, and then PP 2D to 06, the base frequency will be 83.3 kbps. The AT DP command
will report 83 kbps, but the actual baud rate will be 83.3x8/7 = 95.2 kbps.
4. The descriptions for PP 0E bits 3 and 4 were accidentally reversed in the previous data sheet (document
ELM327DSG), and have been corrected.
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