LMK05318B: Reserved Register R220

Benjamin Hirt

Part Number: LMK05318B

Tool/software:

Hello,

I am using the LMK05318B on a design and have been running into an odd issue. It seems when the device first powers on it is working fine and when I read the status page, all registers point to the device is locked.

When I issued a soft reset through the Gui, I found that the device would lose lock and required a hard reset to lock again. Then issuing a soft reset, I would get the same behavior. After some debugging I turned to the input monitor curious if I had an issue there. When I changed a value I caught that the TIC's Pro Gui was writing to register R220 which according to the register page is reserved. Funny enough, if I set R220 with the same value, I never have an issue and the PLL always reports lock even with a soft reset.

Can you comment on what the function of R220 is? The original value was read as "0x00DC 7A" and the gui modified it to "0x00DC 78".

Thanks,

Ben Hirt

over 1 year ago

0 Jennifer Bernal over 1 year ago

TI__Genius 16845 points

Hi Ben,

The R220 is used to configure the PRIREF counter value and is part of the DPLL reference lock settings. This register field gets updated after going through the Wizard then issuing a Run Script in the GUI.

Can you please share your .tcs file?

Regards,

Jennifer

0 Benjamin Hirt over 1 year ago in reply to Jennifer Bernal

Prodigy 20 points

hey Jennifer,

Thanks for the quick reply. Please see the attached TCS file.

LMK05318B_DEBUG.tcs

Ben

0 Jennifer Bernal over 1 year ago in reply to Benjamin Hirt

TI__Genius 16845 points

Hi Ben,

Can you please clarify when you see the register get updated? Is that after enabling the "Frequency Detect Threshold", issuing a Run Script...etc?

0 Benjamin Hirt over 1 year ago in reply to Jennifer Bernal

Prodigy 20 points

hey Jennifer,

I caught the GUI modifying R220 by changing the invalid PPM value. It looks like it wrote to R220 first and then wrote to R211 but I never got to the script step. I changed the value here and went to the status page and saw it cleared the LOL flags.

0 Jennifer Bernal over 1 year ago in reply to Benjamin Hirt

TI__Genius 16845 points

Hi Ben,

These details help. Can you specify the ppm accuracy of your XO input and the PRIREF input?

0 Benjamin Hirt over 1 year ago in reply to Jennifer Bernal

Prodigy 20 points

hey Jennifer,

No problem the PPM accuracy for the local XO is 25ppm. Unfortunately, the input ppm is not easily measured but I believe that it is still on the scale of 20-25ppm as well.

0 Jennifer Bernal over 1 year ago in reply to Benjamin Hirt

TI__Genius 16845 points

Hi Ben,

I was able to test your .tcs file in lab and have no issues with DPLL lock. Note that in lab, I use a near 0ppm reference/XO through the syncing of signal generators.

You will need to widen the frequency detect threshold until the PRIREFVAL_STAT becomes valid, which is what seems you did. Do you have a working configuration now?

The reference counter is also impacted by the reference validation settings such as the freq detect threshold.

Regards,

Jennifer

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LMK05318B: Reserved Register R220