tongyue huang

How can I configure MPC5643L SPI baud rate

Discussion created by tongyue huang on Mar 27, 2016
Latest reply on Mar 29, 2016 by tongyue huang


  Now I configured FMPLL0,1 for 120MHz with 40MHz osc crystal.

Here are two choice for SPI clock:

1.       CGM.SC_DC.B.DE=1;                  //enable clock div

          CGM.SC_DC.B.DIV=11;                //Peripheral clock is 120/(11+1) = 10M;

2.       CGM.OSDC_SC.B.SELCTL = 0X2;         //FMPLL

          CGM.OSDC_SC.B.SELDIV=0X2;          //system clock divide 120/4=30M


The SPI modules registers:DSPI_0.CTR[0].R=0x38087725;  //DBR=0,PBR=0(divide 2),BR=0b0101(divide 32)


My questions:

  1.     SCK baud rate =(Fsys/PBR)*(1+DBR)/BR,

Fsys=120MHz ? 10M ? 30M?

What is the Fsys value? Should I use CGM.SC_DC or  CGM.OSDC_SC in sys clock function?

  2.     Is there any different between Peripheral set 0 clock and Clockout ?

          I configure sys clock,Peripheral set 0 clock and Clockout I can't find them differece.