strange behavior of spi when you change configuratin in delfino dual processor

Hello,

I'm using delfino dual processor

and its SPI.

I change periodically SPI configuration

(see Question )

I notice that when I change SPI configuration

CLK signal execute spurious negative pulse as you see in the image.

my code is

void Spi_PowerOn(Spi spi)
{
	EALLOW; // codice per F2837xD
	if(spi==&SpiaRegs) CpuSysRegs.PCLKCR8.bit.SPI_A = 1;
	if(spi==&SpibRegs) CpuSysRegs.PCLKCR8.bit.SPI_B = 1;
	if(spi==&SpicRegs) CpuSysRegs.PCLKCR8.bit.SPI_C = 1;
	EDIS;
}

void Spi_SetUp(Spi spi, int CLKPOLARITY, int CLK_PHASE, int SPIBRR)
{
	//1880 di SPRUHM8C–December 2013–Revised December 2014

	(*spi).SPICCR.bit.SPISWRESET 	= 0;			// Force reset

	//1900 di SPRUHM8C–December 2013–Revised December 2014

	(*spi).SPICCR.bit.CLKPOLARITY	= CLKPOLARITY;	//polarità clock
	(*spi).SPICCR.bit.SPICHAR		= 7; 			//numero di caratteri (8)

	//1902 di SPRUHM8C–December 2013–Revised December 2014

	(*spi).SPICTL.bit.CLK_PHASE		= CLK_PHASE;	//fase clock
	(*spi).SPICTL.bit.MASTER_SLAVE	= 1;			//master
	(*spi).SPICTL.bit.TALK			= 1;			//TX enable (not High Z)

	//1906 di SPRUHM8C–December 2013–Revised December 2014

	(*spi).SPIBRR					= SPIBRR;

	//1880 di SPRUHM8C–December 2013–Revised December 2014

	(*spi).SPICCR.bit.SPISWRESET	= 1;			// Exit reset

	//asm(" RPT #199||NOP");							// wait 1us @ 200MHz
}
void main()
{
	WatchDog_Disable();
	Flash_Setup();

	Spi_PowerOn(&SpibRegs);

	for(;;)
	{
		Spi_SetUp(&SpibRegs,1,0,49);
		asm(" rpt #199||nop");
		asm(" rpt #199||nop");
		asm(" rpt #199||nop");
	}
}

Please help me, thankyou in advice