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SN65HVD235 bus signals

sruthi uk
Prodigy 120 points

hi,

i tried to transmit CAN frame using CAN module in processor.I connect the oscilloscope to the CAN controller TX pin of transceiver and ground pin and transmit CAN frame is observed in scope. But nothing is coming out of the CANH and CANL pins .What may be the reason??

Also no termination resistor is used between bus lines.

with regards,

sruthy uk.

  • 0
    TI__Guru 62920 points
    Hi Sruthy,

    CAN drivers require termination resistances to be included on the bus in order to function properly. This is because the driver is high-impedance (disabled) during the "recessive" output state, requiring an external differential resistance in order to pull the differential bus voltage close to 0 V. Termination is also a general best practice when communicating over relatively long cables since it serves to match the characteristic impedance of the cable and prevent reflections from degrading signal integrity.

    For HVD235 in particular, you should also make sure neither pin 8 (Rs) nor pin 5 (AB) are pulled high. Both of these pins enable functions that disable the output driver.

    Regards,
    Max