can delimiter

[bbk1707]

In CAN message frame, there are delimiter of 1 bit in both ACK field and CRC field. What are these delimiters for?

[Hooovahh]

Are you asking why the ISO consortium decied to structure the CAN message the way they did?  You'd have to ask them, but if I had to guess maybe it is so the whole frame rounds to the nearest nibble.  With a payload of 0 bytes a standard frame is 5 1/2 bytes in size.

[bbk1707]

I wanted to know the use of the ACK delimiter bit in ACK field.....likewise in the CRC field

[Hooovahh]

Again you'd have to ask ISO what purpose they had in mind for them, but I would say it is so message length is rounded to a nibble, and possibly for a point of reference, so it is easier to find the end of a message.