TMS320F2812 XCLKOUT anomaly.

Kishen Someshwar

Other Parts Discussed in Thread: TMS320F2812

Hello Team,

I have a customer who is using the TMS320F2812 in his design. He is seeing a anomaly in the XCLKOUT pin. Somtimes he gets the XCLKOUT signal and sometimes he does not even though the power-up sequence is the same. Here is what he mentioned:

" I am using TMS320F2812. For some reason, we have intermittent XCLKOUT output (pin 119). sometime it is ON and sometime it is OFF. It happens right after 1.8V input coming to DSP. ( meaning during power on mode). What possible causing the problem.

Attached is the screen shot during power up mode. It sometime shows and not shows XCLKOUT output.

It happens intermittent in current unit, I would say 1 out of 10 tried. It also sometimes happened on other units but not all for them.

Please also see the schematic in the attachment". ( Emailed separately)

I tried to suggest some trouble shooting suggestions but it did not work. I would appreciate your assistance in this matter.

Thank you for your time.

Sincerely,

Kishen

Power_On_Sequence.pdf

over 9 years ago

0 Adam Dunhoft over 9 years ago

TI__Expert 7885 points

Hi Kishen,

1. Does the customer expect to see XCLKOUT toggling after startup?
2. Does the rest of the application work as expected?
3. Is customer using a XTAL to clock the device?
4. Can customer add external clock waveform (XTAL/resonator) to scope capture?
5. Can customer also check XRSn pin state?

To me, it looks like the clock (XTAL) is not starting.

Best Regards,
Adam Dunhoft

0 Adam Dunhoft over 9 years ago in reply to Adam Dunhoft

TI__Expert 7885 points

Hi Kishen,

Please disregard question 1. and 2. as it has come to my attention that XCLKOUT should toggle from startup without application code.

Also disregard 5. as I missed it in your original scope capture.

Questions 3. and 4. are still valid.

Best Regards,
Adam Dunhoft

0 Kishen Someshwar over 9 years ago in reply to Adam Dunhoft

TI__Intellectual 1625 points

Hello Adam,

Attached is the XTAL vs XDSPCLKOUT during power up sequence.

It showed the XTAL worked during no XDSPCLKOUT and with XDSPLKOUT.

Let me know if you need any more detail information.

Sincerely,

Kishen

XTAL vs XDSPCLKOUT.pdf

0 Adam Dunhoft over 9 years ago in reply to Kishen Someshwar

TI__Expert 7885 points

Hello Kishen,

Thank you for the waveforms.

Does the application startup and function properly even when XCLKOUT does not toggle on power up?

Best Regards,
Adam Dunhoft

0 Kishen Someshwar over 9 years ago in reply to Adam Dunhoft

TI__Intellectual 1625 points

Hello Adam,

As requested earlier, Please see the attachment.

The purple is X1/XCLKIN and the red is XDSPCLK out. I sent you both XDSPCLKOUT working and not working.

Sincerely,

Kishen

0 Adam Dunhoft over 9 years ago in reply to Kishen Someshwar

TI__Expert 7885 points

Hello Kishen,

When XCLKOUT does not start, does the application code run as expected or does the device not function properly?

Best Regards,
Adam Dunhoft

0 Kishen Someshwar over 9 years ago in reply to Adam Dunhoft

TI__Intellectual 1625 points

Hello Adam,

The customer does not see the device work when XCLKOUT does not start.

Kishen

0 Adam Dunhoft over 9 years ago in reply to Kishen Someshwar

TI__Expert 7885 points

Hi Kishen,

I noticed that the voltage scale for X1/XCLKIN on the scope when XCLKOUT does not start toggling is 20V per div vs 2V per div on the screen capture when XCLKOUT does start toggling.

Was this done purposely?

Can you take the capture again with the same scope settings?

I'm questioning whether the signals on X1/XCLKIN are the same for both states.

Best Regards,
Adam Dunhoft

0 Kishen Someshwar over 9 years ago in reply to Adam Dunhoft

TI__Intellectual 1625 points

Hello Adam,

I confirmed with the customer. The probe was set x10 on by mistake. For sure, it is 2V because there is no 20V signal input to that board.

Sincerely,
Kishen