C6748 Reset pin

Chris Roed

Hello

I'm using CCS5.4, with an XDS510 jtag debugger and a custom C6748 board. I just got it back and realized that I didn't connect the RESETn pin. Looking at the datasheet... it appears that the device will reset when the pin is low, but there is an internal pull up resistor so the pin *should* be pulled high, and the device *should* be running... I just won't be able to reset it with my pushbutton.

However...I do have access to the RESETOUTn pin, and it is low, meaning the device is in reset.

I have access to the JTAG TRSTn pin as well, and it's tied to ground with a 4.7K resistor, which is how it is configured in the LCDK board. When I try to connect through CCS, it's pulled high until the Connect to Target fails.

Is there anything else I can try?

-Regards

over 11 years ago

0 Chris Roed over 11 years ago

Intellectual 960 points

C6748 datasheet section 5.3.1 "RESET must be maintained active until all power supplies have reached their nominal values."

I suppose this means that if I'm not actively pulling it low, it's going to rise with the rest of the voltage rails (I think it's on the 3.3v rail), and will screw up the POR. Can anyone verify this?

0 Antony Samsunil over 11 years ago in reply to Chris Roed

TI__Expert 4760 points

Hi Chris,

Yes off course you need to initiate the POR by bringing RESET and TRST low at the same time .Basically you need to connect the RESET pin to PMIC or other reset generation circuitry to do this you can’t leave this pin hanging.

Please refer the schematics check list and refer the LCDK schematics for more details.

http://processors.wiki.ti.com/index.php/OMAP-L13x_/_C674x_/_AM1x_Schematic_Review_Checklist

And also refer powering the C6748 application note for more details

http://www.ti.com/lit/an/slva490/slva490.pdf

Regards

Antony

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0 Chris Roed over 11 years ago in reply to Antony Samsunil

Intellectual 960 points

Thanks for the response. We reworked a couple of boards and connected the reset line properly. The board works now.

I had a mislabeled net on my schematic. /shame face

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C6748 Reset pin