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TMS320F2812 not starting up

Stephen weeks
Prodigy 30 points

Other Parts Discussed in Thread: TMS320F2812

So my company has been using these DSPs for years with no issues like this. When it came time for me to do my first design I followed previous designs to keep things simple but when the prototypes came in they wold not startup after programing. After much hair pulling I discovered that the rails need to be sequenced for proper startup so I hacked in some sequencers and it started up properly. Jump into the future and prototype #2 with sequencers build in. Again it programs fine through JTAG but still wouldn't start up, sequencers are working properly POR is working properly yet nothing. I did find that if I externally pull GPIOD5 down then release the processor starts running. This pin is not used in my design thus is not connected to anything. It's also the only pin where this happens, I have lots of other unconnected GPIOs but no others will exhibit  this behavior. Am I missing a startup condition and by chance this one pin and by chance this one GPIO is able to start it up?

  • 0
    TI__Genius 10830 points

    Which power sequencing approach did you use?  Option 1 where you ramp 1V8 then 3V3 or option 2 (recommended) where you ramp 3V3 then 1V8?  How does the timing of the sequencing look on the scope?  How does this compare to Figure 6-6 of TMS320F2812 Digital Signal Processors Data Manual Literature Number: SPRS174R April 2001–Revised May 2010?  What is the XRS(bar) doing during this time?  How does your power down sequencing look comparted to section 6.8 of the same document?  At the moment VDDIO has reached 2V5, what voltage do you see at 1V8 or 1V9 (VDD/VDD1)?

  • 0 in reply to Jason Work
    Prodigy 30 points

    I'm using option 2, ramping 3.3V then 1.8V.I took a grab off the scope. A is 3.3V B is 1.8V. As you can see 1.8V doesn't start to ramp up until several hundred micro seconds after 3.3V passes 2.5V.

    XRS(bar) is held low for ~95ms after power up. Here A is 1.8V B is XRS(bar)

    As for power down XRS(bar) is pulled down when 3.3V drops below 2.8V, this happens ~2.5ms before 1.8V drops below 1.5V.

    A is 3.3, B is XRS.

    A is XRS, B is 1.8V