How to configure MPC5748G Master SPI2 to 40MHz using the SDK with Processor Expert?

[davidanderle]

Hello,

I've been trying to configure SPI2 on the 176-pin package of the MPC5748G to 40MHz clock rate in S32DS v2.1. Although Processor Expert accepts this clock figure, the output clock is capped at 20MHz. What I mean by this is any baud rate I chose above 20MHz will be limited to 20MHz. Setting anything below that works perfectly fine. I am using the recommended external clocks and MPC5748G_SDK_Z4_0 3.0.0 SDK.

It is worth mentioning that I'm using DMA on both Tx and Rx and that my SPI mode is CPOL=0, CPHA=1.

Could someone please help me identify what might be wrong in my setup?

Thanks!

[davidanderle]

Hi PetrS, 

You are right, the DBR bit is not set at all in the driver. I've created a simple patch for the clock prescale calculator and now I can see the 40MHz clock output. Thanks for highlighting this! Is there maybe an opensource git repository I could do a pull request for this code change?

[PetrS · Accepted solution]

Hi,

check how CTAR register is finally configured and if it equals equations in CTAR description. Maybe just DBR is not set, I guess it is not set in the driver at all.

BR, Petr