topic Re: S32K144 SPI baudrate in S32K

S32K144 SPI baudrate

lyz — Thu, 06 Nov 2025 03:15:26 GMT

How do caculate S32K144 SPI Baudrate. How is computational formula？I see that in SDK. As fllow:

realBaudrate = (sourceClockInHz / (s_baudratePrescaler[prescaler] * (scaler + (uint32_t)2U)));

but， I do not understand. please tell me how is computational formula! thanks.

回复： S32K144 SPI baudrate

lyz — Thu, 06 Nov 2025 03:21:14 GMT

I do not understand these:

The SCK period is equal to (SCKDIV+2) cycles of the LPSPI functional clock divided by the Prescaler Value TCR[PRESCALE] configuration.

realBaudrate = (sourceClockInHz / (s_baudratePrescaler[prescaler] * (scaler + (uint32_t)2U)));

Re: S32K144 SPI baudrate

VaneB — Thu, 06 Nov 2025 17:02:20 GMT

Hi @lyz

The SPI baud rate is calculated as:

Baud Rate = (Functional clock / PRESCALE) / (SCKDIV+2)

PRESCALE: Configured in the Transmit Command Register (TCR).

SCKDIV: Configured in the Clock Configuration Register (CCR).

If you find the SDK implementation confusing, refer to section 2.8 of the S32K1xx Series Cookbook. It is a good starting point for understanding how to configure the LPSPI.

BR, VaneB

Re: S32K144 SPI baudrate

lyz — Fri, 07 Nov 2025 01:25:00 GMT

ok, thank you.

Re: S32K144 SPI baudrate

lyz — Fri, 07 Nov 2025 12:13:06 GMT

Project from example config delay in SDK, as follow. Why? I do not understand:

in S32K1xx Series Cookbook.

so,

How config SCKPCS of SCK-to-PCS Delay？

How config PCSSCK of PCS-to-SCK Delay？

How config DBT of Delay Between Transfers？

Re: S32K144 SPI baudrate

VaneB — Fri, 07 Nov 2025 22:03:53 GMT

Hi @lyz

The bestScaler is used to configure delay registers because these delays scale with the SPI clock. Applying a right shift by 2 (>> 2U, equivalent to dividing by 4) ensures the delay values remain proportional to the baud rate without being excessively large, providing balanced timing margins for PCS-to-SCK, SCK-to-PCS, and Delay Between Transfers.

Re: S32K144 SPI baudrate

lyz — Sun, 09 Nov 2025 01:12:27 GMT

I understand logic in SDK code, but the logic (>> 2U, equivalent to dividing by 4) refence where describe. The reference of S32K-RM.pdf provide of the logic, as follow:

so, What is the configuration logic, about SCKPCS / PCSSCK / and PCSSCK ?

How config SCKPCS of SCK-to-PCS Delay？

How config PCSSCK of PCS-to-SCK Delay？

How config DBT of Delay Between Transfers

in detail.

Re: S32K144 SPI baudrate

lyz — Mon, 10 Nov 2025 02:56:17 GMT

hello, @VaneB

Project from example config delay in SDK, as follow

the logic (>> 2U, equivalent to dividing by 4) refence where describe, Why?

I fell that it is diffent the logic whitch the reference of S32K-RM.pdf provide, as follow:

I do not understand!

What is the configuration logic, about SCKPCS / PCSSCK / and PCSSCK ?

Please tell me.

Thank you very much!

Re: S32K144 SPI baudrate

VaneB — Mon, 10 Nov 2025 17:41:01 GMT

Hi @lyz

The use of >> 2U (equivalent to dividing by 4) for delay calculations is not documented in the reference manual as a strict formula. Instead, it originates from SDK timing guidelines intended to ensure proper functionality.