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Baud rates for DSPI in MPC5777M

Question asked by yalamanda dosakyala on Apr 21, 2017
Latest reply on Apr 28, 2017 by Petr Stancik

Hi Martin Kovar , I am going to develop SPI driver for MPC5777M , I have seen your example for this. But I want to use different baud rates like 1MBPS,2MBPS, 4 ,8 ,10 , 20  and 40 MBPS.I am able to configure  2MBPS ,4 MBPS, 8MBPS, 10MBPS and communication is happening fine. But for 20 and 40 are not working (MSTR -> SLAVE data is transferring correctly but SLAVE ack received at MSTR is different value.)

 

The below are my configuration settings for different baud rates. I am using 80MHZ clock freq.

 

/*
     * FMSZ (Frame size) = 0xF
     * PBR (Baud Rate Prescaler) = 0x2 - Baud Rate Prescaler value is 5
     * CSSCK(PCS to SCK Delay Scaler) = 1 Delay Scaler value is 4
     * BR (Baud Rate Scaler) = 4 - Baud Rate Scaler value is 16
     * DBR (Double Baud Rate) = 0
     *
     * SCK baud rate = (fsys/PBR) * [(1+DBR)/BR]
     * SCK baud rate = (80MHz/5) * [(1+0)/16] = 1MHz
     */

 

      DSPI_3.MODE.CTAR[0].R = 0x78021004;-->1MBPS
     *DSPI_3.MODE.CTAR[0].R = 0x78011004;-->2MBPS
     *DSPI_3.MODE.CTAR[0].R = 0x78011003;-->4MBPS
     *DSPI_3.MODE.CTAR[0].R = 0x78011001;-->8MBPS
     *DSPI_3.MODE.CTAR[0].R = 0x78021000;-->10MBPS

 

 Can you please help me how to configure CTAR for 20 and 40 mbps baudrates.

 

I have one more doubt that what is the  Maximum baudrate can we configure ?

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