buscandigital-logic
I am reading data sheets on the LIN bus, but apparently the same terminology is used for CAN.
What does "recessive" and "dominant" stand for, e.g http://hw-server.com/products/rs_optika/prevodniky_optika.html ?
How relate these terms to "low" and "high", or 0 and 1?
There's no rocket science in CAN transeivers.
Normally, reference voltages are achieved using a simple voltage drop circuit or a linear volatage regulator.
Note, as there may be a large voltage drop between transmitter and receiver grounds (80 V AFAIK) there's no need for precisely 2.5 V. Low-voltage transceivers use a lower common-mode voltage.
So only a differential voltage of ±0.5 V is actually regulated, and the common mode voltage can be set by a simple voltage divider.
There are some interesting schematics in the article Isolated CAN Transceiver Assures Robust Fieldbus Design.
Note the diodes feeding CAN-Low and CAN-High. Together with output transistors they give about a 1.5 V drop. (They also protect the transistors from reverse current.)
Best Answer
Dominant is 0. Recessive is 1. Dominant applies to 0 because if two arbitration ID's are being transmitted at the same time and the first 4 bits are the same and the fifth is 0 for one of them and 1 for the other, the ID with the 0 will end up being transmitted. Transmission of the message with the larger arbitration ID will be tried again after the other message is done.