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What are comprehensive differences between J1939/Extended CAN vs. J1939/CAN FD?

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Oct 30, 2014
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How does messaging work in CAN FD? How are PGNs and SPNs defined for CAN FD?

For Extended CAN, SAE J1939-71 defines PGNs and SPNs. All the PGNs and SPNs defined in SAE J1939-71 don't apply to CAN FD? For example, in SAE J1939-71 PGN 65267 is Vehicle Position. There are two SPN's in this PGN. Each SPN is 4 bytes. This makes 8 byte data field. How to construct some message like Vehicle Position in CAN FD?

If some Electronic Control Unit (ECU) is communicating over J1939 with extended CAN, how to determine if this ECU needs capability of CAN FD?

SAE J1939-21, Transport layer protocol defines messages that have data field more than 8 bytes. Why not just use SAE J1939-21 to send large size messages? Is CAN FD faster?

Is data field size the only difference between CAN FD and extended CAN? Does 8 times larger data field makes CAN FD much faster than extended CAN?

What code changes are needed to update from J1939/extended CAN to J1939/CAN FD ? is different J1939 stack needed? Are different CAN drivers needed? If yes, please provide comparison of J1939 stack changes and CAN driver changes.

What are other significant differences between J1939/extended CAN and J1939/CAN FD ?

I meant What are comprehensive differences between J1939/Classical CAN vs. J1939/CAN FD?

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