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TMS470 & HALCoGen LPO calculation issue

Mathew Maher49
Expert 2125 points

Other Parts Discussed in Thread: HALCOGEN

Hi,

We're trying to setup a TMS470 to run it's DCAN peripheral off the LPO HF, however we've been finding all sorts of problems with the bit timing going out?

We are setting the DCAN to generate 500kbps baud rate. This works fine when driven from the OSC (16Mhz), but swapping over to the HF LPO (10Mhz), it generates a 543kbps CAN bus.

Looking at the datasheet, it suggests the HF LPO is nominal 12MHz, but HalCoGen bases everything around 10MHz - could this be the sources of the error?

Otherwise, can you advise on the tolerance of the LPO HF - is it possible it's just not accurate enough to drive a CAN bus?

Thanks

Mat

 

  • 0
    TI__Guru**** 200526 points

    Hi Mat,

    #1: The LPO for TMS470M is 12MHz rather than 10MHz. You use wrong (generated for 10Mhz) bit timing parameters (Sync_Seg, TSeg1, TSeg2, and BRP) for 12MHz internal clock.  

    #2: The LPO is not accurate enough for DCAN application. I suggest to use the external OSC for DCAN.

    Regards,

    QJ