dma

DMA例程

;-----------------------------------------------------------------------------------------
;        异步写模块： 从模块读数据从串口发出
;-------------------------------------------------------------------------------------   
	       PWR         EQU     5
           PRD         EQU     6
           PWAIT       EQU     7
           DMAING      EQU     0
           DMADIR      EQU     1
           FIFOEMPTY   EQU     2
           FIFOFULL    EQU     3
           DMACS       EQU     4
           DMAOE       EQU     5
           PKTEND      EQU     6
		   DMAWR       EQU     6
		   DMARD       EQU     7
;-----------------------------------------------------------------------------	
           ORG      0000H
           AJMP     MAIN
           ORG      0040H
MAIN:      MOV      TMOD,     #20H	    ;TIMER1工作与8位自装载模式
           MOV      SCON,     #60H	 	;串口工作与模式1
           MOV      PCON,     #00H
           MOV      TL1,      #0FDH		 ;波特率9600
           MOV      TH1,      #0FDH
           CLR      EA
           MOV      SP,        #70H
           SETB     TR1
		   MOV      DPTR,       #0CFFFH				  ;为不影响P2口，写地址为0CFFF，此处也可用
;----------------------------------------------------------
WAITRX:    CLR      P3.DMACS
           JNB      P2.DMAING,  WAITRX
           JB       P2.DMADIR,    WAITRX
           JNB      P2.FIFOEMPTY,  WAITRX
           CLR      P2.DMAOE
           NOP
		   MOVX     A,     @DPTR					 ;此处也可用 MOVX  A， @R0指令，此时写地址为0FF，
		   NOP
		   MOV      SBUF,   A
		   ACALL    DELAY1MS
		   AJMP     WAITRX
;---------------------------------------------------------
DELAY1MS:  MOV      R3,   5
DELAY1:    MOV      R4,   100
DELAY0:	   DJNZ     R4,   DELAY0
           DJNZ     R3,   DELAY1
		   RET
;---------------------------------------------------------	 
           END