CAN Transceiver interface with Microcontroller Freescale SPC5674F

The SN65HVD256 is a 5V CAN transceiver with 3.3V compatible inputs.  The TXD and S pin input thresholds are VIL = <=0.8V and VIH<= 2V.  There is a second supply pin called Vrxd on pin 5 to level shift the output voltage of the RXD output pin to the host uP for devices that do not have 5V tollerant inputs (which would be the issue for example when using the SN65HVD255 5V CAN transceiver).  This level shifting is specified from 2.8V to 5.5V on the HVD256 thus giving wide margin to directly interface to most 3.3V I/O uPs without needed external circuits on the logic side.  However if the devices will be used in a very noisy environment standard noise filtering, current limiting and other schemes may be employed to ensure the cleanest signals possible between the uP and the SN65HVD256.  Additionally a good practice is to put protection and filtering footprints on your PCB for the CAN Bus side so that that if these are necessary it is a simple matter to populate and use them instead of having to re-design a PCB.  Examples of both I/O pin protection and filtering and bus side filtering and protection are documented in the SN65HVD255 CAN EVM which is also a sort of generic CAN EVM and could be re-populated with the SN65HVD256 and a few jumper changes.  Info on the EVM and it's recommended design practices may be found at:  http://www.ti.com/tool/sn65hvd255devm  .  The other point to consider since CAN is a bus is where the termination resistors are for each end of the bus.  These may either be PCB population options, or done in the CAN cables themselves, this is also highlighted in the CAN EVM guide. 

Depending on your application requirements you may also want to consider looking at the 3.3V CAN transceivers:  SN65HVD230, 231, 232, 233, 234, 235.  Closest to the the HVD256 is the SN65HVD234. 

You may find additinal CAN information at www.ti.com/can and below is a list of TI app notes & links regarding CAN transceivers and bus applicaitons.

-- Scott