Many universities and large automotive companies subscribe to standards databases like:
ISO 11898-2 is the international standard governing the for the Controller Area Network (CAN) bus. It defines the physical layer specifications—such as cable types, electrical signal levels, and node requirements—that allow electronic control units (ECUs) in road vehicles to communicate reliably. Accessing the PDF Document iso 11898-2 pdf download
ISO 11898-2 is the international standard that specifies the sublayer for the Controller Area Network (CAN). electrical signal levels
Searching for a "free" ? You’re likely neck-deep in a project involving High-Speed CAN (Controller Area Network) physical layers. iso 11898-2 pdf download