What is the intrinsic relationship between the SPN value in the SAE1929 protocol and the data length and start bit position/byte?

星YUE点灯

Hello everyone, for the initial study of SAE1939 protocol, thank you for your help. Please forgive me for any mistakes in the expression. For example, the figure above is obtained from the query of SAE1939-71. But I have always wondered whether the value of SPN itself is related to the starting position of the bit and the data length? Can it be obtained through numerical analysis? If I only know Png65169, SPN1239. Can I get the starting position (1.1) and length (2 bits) through this data analysis instead of looking up the table? So now I really want to know if there is really a connection between them, but I don’t know it because I am not well-educated. Instead of just looking up the table to get it.

星YUE点灯

First time posting, don't know why the picture didn't show up. I'll add it here manually. Sorry for that. Png 65169-Fuel Leakage-FL Transmission Cycle Rate: 1s Data Length: 8 bytes Data Page: 0 PDU Format: 254 PDU Specific: 145 Default Priority Value: 7 Parameter Group Number: 65169 (00FE91) Bit Start Position/Byte Length SPN Description SPN 1.1 2-bit Fuel Leakage 1 1239 1.3 2-bit Fuel Leakage 2 1240

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