TCXO frequency & CPU clock tuning for best PPS precision

[Yegor]

Hello — please help with the following questions about parameters:

How should I correctly configure the TCXO frequency parameter $PSTMGETPAR,1245 (TCXO Frequency)?
How should I correctly configure the CPU clock speed parameter $PSTMGETPAR,1130 (CPU clock speed)?
To improve PPS accuracy, is it correct that the CPU clock speed should be set equal to the PPS Clock?
What are the maximum supported values for the PPS Clock and for the CPU clock?

[GalaxyQuest]

Can you please tell me which product you are using?

If you are using a Teseo module then you would not need to manipulate CDB-245 register setting.

However you can modify CDB-130[b4...b6] register setting if you want to increase clock speed. 

From B4 to B6
0 = 1
1 = 2
3 = 4
Allow setting the CPU clock divisor factor

[Yegor]

Module Quectel L26-T

[GalaxyQuest]

Hi,

Since you are using the module with the TCXO already included,  the TXCO frequency setting is typically set by module manufacturer. You would not need to modify this. Can you please check with Quectel on the setting? However, on CPU clock speed you can change the CDB-130 register setting if you want a lower clock divisor.

Thanks.

[Yegor]

Could you please clarify what are the potential drawbacks of increasing the CPU clock frequency (i.e. setting a lower clock divisor)?

Are there any recommended limits or guidelines for this setting?

[GalaxyQuest · Accepted solution]

Running CPU at a higher clock speed can increase current consumption.

If you are outputting messages at a higher fix rate or outputting a lot of NMEA messages, then it is best you can run at a higher clock rate.