Reference: Bosch CAN 2.0 A & B Specifications, Section: PARTA, Data Frame, Data Field, Page: 13
DATA FIELD
The DATA FIELD consists of the data to be transferred within a DATA FRAME. It can
contain from 0 to 8 bytes, which each contain 8 bits which are transferred MSB first.
It should noted, the CAN 2.0 A/B specification (ISO 11898) makes no reference to the endianness of the underlying architecture of the device for which CAN has been implemented, as the previous two members have indicated. The CAN 2.0 A/B provide only a baseline protocol of the ISO/OSI layer model, layers 1 and 2, by which to implement an overlying protocol, layer 7 (application layer), such as CANopen, DeviceNET, J1939, etc.