C2000 8bit spi cycle

//###########################################################################
//
//!  \addtogroup f2806x_example_list
//!  <h1>SPI Digital Loop Back(spi_loopback)</h1>
//!
//!  This program uses the internal loop back test mode of the peripheral. 
//!  Other then boot mode pin configuration, no other hardware configuration
//!  is required. Interrupts are not used.
//!
//!  A stream of data is sent and then compared to the received stream.
//!  The sent data looks like this: \n
//!  0000 0001 0002 0003 0004 0005 0006 0007 .... FFFE FFFF \n
//!  This pattern is repeated forever.
//!  
//!  \b Watch \b Variables \n     
//!  - \b sdata , sent data
//!  - \b rdata , received data
//		
////###########################################################################		
// $TI Release:  $
// $Release Date:  $
//#############################################################################

#include "DSP28x_Project.h"     // Device Headerfile and Examples Include File

// Prototype statements for functions found within this file.
void spi_xmit(Uint16 a);
void spi_fifo_init(void);
void spi_init(void);
void error(void);

void main(void)
{
   Uint16 sdata;  // send data
   Uint16 rdata;  // received data
   
// Step 1. Initialize System Control:
// PLL, WatchDog, enable Peripheral Clocks
// This example function is found in the F2806x_SysCtrl.c file.
   InitSysCtrl();

// Step 2. Initalize GPIO: 
// This example function is found in the F2806x_Gpio.c file and
// illustrates how to set the GPIO to it's default state.
// InitGpio();  // Skipped for this example  
// Setup only the GP I/O only for SPI-A functionality
// This function is found in F2806x_Spi.c
   InitSpiaGpio();

// Step 3. Clear all interrupts and initialize PIE vector table:
// Disable CPU interrupts 
   DINT;

// Initialize PIE control registers to their default state.
// The default state is all PIE interrupts disabled and flags
// are cleared.  
// This function is found in the F2806x_PieCtrl.c file.
   InitPieCtrl();

// Disable CPU interrupts and clear all CPU interrupt flags:
   IER = 0x0000;
   IFR = 0x0000;
   
// Initialize the PIE vector table with pointers to the shell Interrupt 
// Service Routines (ISR).  
// This will populate the entire table, even if the interrupt
// is not used in this example.  This is useful for debug purposes.
// The shell ISR routines are found in F2806x_DefaultIsr.c.
// This function is found in F2806x_PieVect.c.
   InitPieVectTable();
	
// Step 4. Initialize all the Device Peripherals:
// This function is found in F2806x_InitPeripherals.c
// InitPeripherals(); // Not required for this example
   spi_fifo_init();	  // Initialize the Spi FIFO
   spi_init();		  // init SPI

// Step 5. User specific code:
// Interrupts are not used in this example. 
   sdata = 0x0000;							
   for(;;)
   {    
     // Transmit data
	     spi_xmit(0);
	     spi_xmit(0);
	     spi_xmit(0);
	     spi_xmit(1);
     // Wait until data is received
     while(SpiaRegs.SPIFFRX.bit.RXFFST !=1) { } 			
     // Check against sent data
     rdata = SpiaRegs.SPIRXBUF;				
     if(rdata != sdata) error();
     sdata++;
   }
} 	

// Step 7. Insert all local Interrupt Service Routines (ISRs) and functions here:	

void error(void)
{
   __asm("     ESTOP0");						// Test failed!! Stop!
    for (;;);
}

void spi_init()
{    
	SpiaRegs.SPICCR.all =0x0007;	             // Reset on, rising edge, 16-bit char bits
	SpiaRegs.SPICTL.all =0x0006;    		     // Enable master mode, normal phase,
                                                 // enable talk, and SPI int disabled.
	SpiaRegs.SPIBRR =0x007F;									
    SpiaRegs.SPICCR.all =0x009F;		         // Relinquish SPI from Reset   
    SpiaRegs.SPIPRI.bit.FREE = 1;                // Set so breakpoints don't disturb xmission
}

void spi_xmit(Uint16 a)
{
    SpiaRegs.SPITXBUF=a;
}    

void spi_fifo_init()										
{
// Initialize SPI FIFO registers
    SpiaRegs.SPIFFTX.all=0xE040;
    SpiaRegs.SPIFFRX.all=0x2044;
    SpiaRegs.SPIFFCT.all=0x0;
}  

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// No more.
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