近来无事，写了一个dma与uart配合收发数据的小程序，开发板用的是以前博文上介绍的mcf52235开发板，软件开发环境cw7.0.

dma_uart.rar

#include "dma.h"
#include "mcf52235.h"

char receive[64];

void uart0_init(uint16 baudrate)

{
uint32 div,SYS_CLOCK;
SYS_CLOCK=60000000;
MCF_GPIO_PUAPAR=MCF_GPIO_PUAPAR_UTXD0_UTXD0|MCF_GPIO_PUAPAR_URXD0_URXD0;

//Reset Transmitter Receiver Mode Register

MCF_UART0_UCR|=(0 |MCF_UART_UCR_RESET_TX
|MCF_UART_UCR_RESET_RX
|MCF_UART_UCR_RESET_MR);

//No parity,8bit data

MCF_UART0_UMR1=(0
|MCF_UART_UMR_PM_NONE
|MCF_UART_UMR_BC_8);
//1bit stop

MCF_UART0_UMR2=(0|MCF_UART_UMR_CM_NORMAL|MCF_UART_UMR_SB_STOP_BITS_1);

//Set Rx and Tx buad by SYSTERM CLOCK

MCF_UART0_UCSR=(0|MCF_UART_UCSR_RCS_SYS_CLK|MCF_UART_UCSR_TCS_SYS_CLK);

//Mask all UART interrupts

MCF_UART0_UIMR=0;

//set buad rate

div=(SYS_CLOCK/32/baudrate);
MCF_UART0_UBG1=(unsigned char)(div>>8);
MCF_UART0_UBG2=(unsigned char)(div&0x00ff);
//Enable Tx/Rx
MCF_UART0_UCR=(0|MCF_UART_UCR_TX_ENABLED|MCF_UART_UCR_RX_ENABLED);
}

void DMA_init(void)

{

char *decadd=receive;
char i;
for(i=0;i<64;i++)
{
receive[i]=0;
}
MCF_SCM_DMAREQC=MCF_SCM_DMAREQC_DMAC0(0x8);//UART0 receive
//source address register
MCF_DMA0_SAR= 0x4000020C;
//destination address register
MCF_DMA_DAR(0)=(uint32)decadd;
//byte count
MCF_DMA0_BCR=64;
MCF_DMA0_DCR=MCF_DMA_DCR_INT //interrupt enable
|MCF_DMA_DCR_EEXT //enable external request
|MCF_DMA_DCR_CS //force a single read/write transfer per request
|MCF_DMA_DCR_SSIZE(MCF_DMA_DCR_SSIZE_BYTE)
|MCF_DMA_DCR_DINC
|MCF_DMA_DCR_DSIZE(MCF_DMA_DCR_DSIZE_BYTE);

//UART0 read
MCF_SCM_PACR2=MCF_SCM_PACR_ACCESS_CTRL1(5);

//read/write
MCF_SCM_GPACR0=MCF_SCM_GPACR_ACCESS_CTRL(6);

//interrupt enable
MCF_INTC0_IMRL&=~MCF_INTC_IMRL_MASKALL;
MCF_INTC0_IMRL&=~MCF_INTC_IMRL_INT_MASK9;

//channel 0
MCF_INTC0_ICR09=MCF_INTC_ICR_IP(3)+MCF_INTC_ICR_IL(2);

}

void uart0_putchar(char c)

{

//Wait until space is available in the FIFO
while (!(MCF_UART0_USR&MCF_UART_USR_TXRDY)) { ; }

//Send the character
MCF_UART0_UTB = (unsigned char)c;

}

unsigned char uart0_getchar()

{

//Wait until character has been received
while (!(MCF_UART0_USR & MCF_UART_USR_RXRDY))
{ };

return MCF_UART0_URB;

}

void uart0_putstr(char *str)

{

while(*str!=0) { uart0_putchar(*str++); }

}

__declspec(interrupt:0) void DMA0_handler(void)//source 9

{

uint8 int_status = MCF_DMA0_DSR;

if(int_status & MCF_DMA_DSR_DONE)

{

if(int_status & MCF_DMA_DSR_CE) { uart0_putstr("configuration error\n"); }

else if(int_status & MCF_DMA_DSR_BED) { uart0_putstr("destination bus error\n"); }

else if(int_status & MCF_DMA_DSR_BES) { uart0_putstr("source bus error\n"); }

else {

uart0_putstr("dma0 transfer done\n");

uart0_putstr(receive);

}

//clear DMA0 interrupt

MCF_DMA0_DCR&=~MCF_DMA_DCR_EEXT;

MCF_DMA0_DSR |= MCF_DMA_DSR_DONE;

MCF_DMA_DAR(0)=(uint32)receive;

MCF_DMA0_BCR=64;

MCF_DMA0_DCR|=MCF_DMA_DCR_EEXT;

}

if(int_status & MCF_DMA_DSR_BSY) { uart0_putstr("busy\n"); }

if(int_status & MCF_DMA_DSR_REQ) { uart0_putstr("transfer remaining but channel not selected\n");}

}