SPI (SSC) Slave Mode

[#1]

Hi,

I tried to configure a XMC1300 to work in SPI-Slave-Mode by setting the USIC-registers in this way:
(since I just want to receive data, I didn't initialise the data output pin)

#include 

void USIC0_Init(void)
{
	 //Kernel State Configuration Register - Module Enable + Bit Protection for MODEN
	  USIC0_CH1->KSCFG |= (1 << USIC_CH_KSCFG_MODEN_Pos) | (1 << USIC_CH_KSCFG_BPMODEN_Pos);

	  //Configuration of USIC Input Stage
	 WR_REG(USIC0_CH1->DX0CR, USIC_CH_DX0CR_DSEL_Msk, USIC_CH_DX0CR_DSEL_Pos, 1); //MOSI: P1.2
	 WR_REG(USIC0_CH1->DX0CR, USIC_CH_DX0CR_INSW_Msk, USIC_CH_DX0CR_INSW_Pos, 1);

 	 WR_REG(USIC0_CH1->DX1CR, USIC_CH_DX1CR_DSEL_Msk, USIC_CH_DX1CR_DSEL_Pos, 1); //SCKL: P0.8
	 WR_REG(USIC0_CH1->DX1CR, USIC_CH_DX1CR_INSW_Msk, USIC_CH_DX1CR_INSW_Pos, 1);

	 WR_REG(USIC0_CH1->DX2CR, USIC_CH_DX2CR_DSEL_Msk, USIC_CH_DX2CR_DSEL_Pos, 1); //SS:   P0.9
	 WR_REG(USIC0_CH1->DX2CR, USIC_CH_DX2CR_INSW_Msk, USIC_CH_DX2CR_INSW_Pos, 1);

 	  //Configuration of USIC Shift Control
	  //Transmission Mode (TRM) = 1
	  WR_REG(USIC0_CH1->SCTR, USIC_CH_SCTR_TRM_Msk, USIC_CH_SCTR_TRM_Pos, 1);

 	 //Configuration of Channel Control Register
	 WR_REG(USIC0_CH1->CCR, USIC_CH_CCR_MODE_Msk, USIC_CH_CCR_MODE_Pos, 1);
	 WR_REG(USIC0_CH1->CCR, USIC_CH_CCR_AIEN_Msk, USIC_CH_CCR_AIEN_Pos, 1);
}

int main(void)
{
        uint32_t buffer = 0;
 	while(1)
	{
		buffer = USIC0_CH1->RBUF0;
		//buffer = USIC0_CH1->RBUF1;
	}
	return 0;
}

Unfortunately, I can't receive the data I'm sending with a PIC24F by Microchip (Master)...
I watched the USIC-registers while debugging and after the PIC had sent 0xAA they looked like this:

http://s14.directupload.net/file/d/3331/tzwxadmk_jpg.htm

according to the RBUFSR (RBUFSR01) register, a "protocol related error" occured but what's that supposed to mean?
Maybe I forget something in my USIC settings...
Can anybody help me?

[#2]

Hi TomTurbo,

From your initialization, everything looks alright.
Did you disable the clock gating of the USIC module?
You should have something like the below code before calling USIC0_Init();

SCU_GENERAL->PASSWD = 0x000000C0UL;
SCU_CLK->CGATCLR0 |= 0x00000008;		// disable USIC clock gating
while((SCU_CLK->CLKCR)&0x40000000UL);
SCU_GENERAL->PASSWD = 0x000000C3UL;

USIC0_Init();

rgds,
Rou

[#3]

Hi Rou,

thanks for the hint, I forget those clock seetings...the XMC received something but the errors are still the same:


Regardless of what I'm sending, the values of RBUF and RBUF0 are always 0x1:confused:

[#4]

Hi TomTurbo,

Instead of reading directly from RBUF0 or RBUF1, I would suggest you to read from RBUF only.
Perhaps something like this:

  while((USIC0_CH1->PSR_SSCMode & USIC_CH_PSR_SSCMode_AIF_Msk)==0);  //   Wait until alt. received flag is set 
  USIC0_CH1->PSCR     |= USIC_CH_PSR_SSCMode_AIF_Msk;                //   Clear flag
  buffer = USIC0_CH1->RBUF;

rgds,
Rou