[讨论] 在sci_loopback_int例程中，是怎样进入发送中断和接收中断的？

我最近在学28027,恰好看到Sci，和28335是非常类似的，但是看controlsuite里面的例程，有一点疑惑想问：在sci_loopback_int例程中，是怎样进入发送中断和接收中断的？

我本来觉得接收中断应该是我们在串口输入一个字符，点击发送就触发了（这里的话因为是Loopback,所以进入发送中断后，发送数据，就进入接收中断），但发送中断是怎么进入的就非常不理解了。


看到有说法是说把Sci初始化后就有定时器进行计时，到一定数后即触发中断，如果是这样，那定时器的配置在初始化中似乎并没有体现。


也有说法是根据中断标志位来进入中断，但似乎初始化函数里并没有把中断标志置1.

此外，还有一个问题，用Sci每次接收的是一个字符，那如果我希望接收输入的一个两位数，来改变程序中的某个变量值，应该怎么编程比较合理呢？

1.发送中断时28027发送字符才进入的。
2.如果需要接收两位数，你需要设置一个帧头，最好也有桢尾，中间放上你要加的数据。

谢谢！但是针对第一个问题，对于sci_loopback_int的例程还是不太理解，因为主程序中并没有发送字符的语句，那第一次中断是如何进入的呢？

例程代码如下：




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



#define CPU_FREQ         40E6        // Default = 40 MHz. Change to 60E6 for 60 MHz devices

#define LSPCLK_FREQ CPU_FREQ/4

#define SCI_FREQ         100E3

#define SCI_PRD         (LSPCLK_FREQ/(SCI_FREQ*8))-1



// Prototype statements for functions found within this file.

interrupt void sciaTxFifoIsr(void);

interrupt void sciaRxFifoIsr(void);

interrupt void scibTxFifoIsr(void);

interrupt void scibRxFifoIsr(void);

void scia_fifo_init(void);

void scib_fifo_init(void);

void error(void);



// Global variables

Uint16 sdataA[2];    // Send data for SCI-A

Uint16 rdataA[2];    // Received data for SCI-A

Uint16 rdata_pointA; // Used for checking the received data



void main(void)

{

   Uint16 i;



// Step 1. Initialize System Control:

// PLL, WatchDog, enable Peripheral Clocks

// This example function is found in the DSP2802x_SysCtrl.c file.

   InitSysCtrl();



// Step 2. Initalize GPIO:

// This example function is found in the DSP2802x_Gpio.c file and

// illustrates how to set the GPIO to it's default state.

// InitGpio();

// Setup only the GP I/O only for SCI-A and SCI-B functionality

// This function is found in DSP2802x_Sci.c

   InitSciGpio();



// 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 DSP2802x_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 DSP2802x_DefaultIsr.c.

// This function is found in DSP2802x_PieVect.c.

   InitPieVectTable();



// Interrupts that are used in this example are re-mapped to

// ISR functions found within this file.

   EALLOW;        // This is needed to write to EALLOW protected registers

   PieVectTable.SCIRXINTA = &sciaRxFifoIsr;

   PieVectTable.SCITXINTA = &sciaTxFifoIsr;

   EDIS;   // This is needed to disable write to EALLOW protected registers



// Step 4. Initialize all the Device Peripherals:

// This function is found in DSP2802x_InitPeripherals.c

// InitPeripherals(); // Not required for this example

   scia_fifo_init();  // Init SCI-A



// Step 5. User specific code, enable interrupts:



// Init send data.  After each transmission this data

// will be updated for the next transmission

   for(i = 0; i<2; i++)

   {

      sdataA = i;

   }



   rdata_pointA = sdataA[0];

// Enable interrupts required for this example

   PieCtrlRegs.PIECTRL.bit.ENPIE = 1;   // Enable the PIE block

   PieCtrlRegs.PIEIER9.bit.INTx1=1;     // PIE Group 9, INT1

   PieCtrlRegs.PIEIER9.bit.INTx2=1;     // PIE Group 9, INT2

   IER = 0x100;        // Enable CPU INT

   EINT;



// Step 6. IDLE loop. Just sit and loop forever (optional):

        for(;;);



}



void error(void)

{

    asm("     ESTOP0"); // Test failed!! Stop!

    for (;;);

}



interrupt void sciaTxFifoIsr(void)

{

    Uint16 i;

    for(i=0; i< 2; i++)

    {

           SciaRegs.SCITXBUF=sdataA;     // Send data

        }



    for(i=0; i< 2; i++)                 //Increment send data for next cycle

    {

           sdataA = (sdataA+1) & 0x00FF;

        }



        SciaRegs.SCIFFTX.bit.TXFFINTCLR=1;        // Clear SCI Interrupt flag

        PieCtrlRegs.PIEACK.all|=0x100;      // Issue PIE ACK

}



interrupt void sciaRxFifoIsr(void)

{

    Uint16 i;

        for(i=0;i<2;i++)

        {

           rdataA=SciaRegs.SCIRXBUF.all;         // Read data

        }

        for(i=0;i<2;i++)                     // Check received data

        {

           if(rdataA != ( (rdata_pointA+i) & 0x00FF) ) error();

        }

        rdata_pointA = (rdata_pointA+1) & 0x00FF;



        SciaRegs.SCIFFRX.bit.RXFFOVRCLR=1;   // Clear Overflow flag

        SciaRegs.SCIFFRX.bit.RXFFINTCLR=1;   // Clear Interrupt flag



        PieCtrlRegs.PIEACK.all|=0x100;       // Issue PIE ack

}



void scia_fifo_init()

{

   SciaRegs.SCICCR.all =0x0007;   // 1 stop bit,  No loopback

                                  // No parity,8 char bits,

                                  // async mode, idle-line protocol

   SciaRegs.SCICTL1.all =0x0003;  // enable TX, RX, internal SCICLK,

                                  // Disable RX ERR, SLEEP, TXWAKE

   SciaRegs.SCICTL2.bit.TXINTENA =1;

   SciaRegs.SCICTL2.bit.RXBKINTENA =1;

   SciaRegs.SCIHBAUD = 0x0000;

   SciaRegs.SCILBAUD = SCI_PRD;

   SciaRegs.SCICCR.bit.LOOPBKENA =1; // Enable loop back

   SciaRegs.SCIFFTX.all=0xC022;

   SciaRegs.SCIFFRX.all=0x0022;

   SciaRegs.SCIFFCT.all=0x00;



   SciaRegs.SCICTL1.all =0x0023;     // Relinquish SCI from Reset

   SciaRegs.SCIFFTX.bit.TXFIFOXRESET=1;

   SciaRegs.SCIFFRX.bit.RXFIFORESET=1;



}



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