max549.asm

串行DA

                ORG   0000H
                AJMP  MAIN
                ORG   0100H
                CS    EQU   P2.7    ;片选输入
                SCLK  EQU   P2.5    ;时钟同步输入端，SCLK上升沿串行输入数据DIN移入内部16位寄存器内
                DIN   EQU   P2.6    ;数据输入端

        MAIN:    MOV   SP,#60H
        FDOWN:   CLR   CS
        F11:     MOV   R7,#08H
                 MOV   A,#255
        LOOP2:   RLC   A
                 MOV   DIN,C
                 LCALL PULSE
                 DJNZ  R7,LOOP2
                 CLR   CS
                 NOP
                 SETB  CS
                 LCALL T01MS
                 
                 MOV   R7,#08H
                 MOV   A,#100
        LOOP3:   RLC   A
                 MOV   DIN,C
                 LCALL PULSE
                 DJNZ  R7,LOOP3
                 CLR   CS
                 NOP
                 SETB  CS
                 LCALL T01MS
                 AJMP  F11

         PULSE:  SETB   SCLK
                 MOV   R3,#2
         PULS1:  DJNZ  R3,PULS1
                 CLR   SCLK
                 MOV   R3,#2
         PULS2:  DJNZ  R3,PULS2
                 RET

         T01MS:  MOV     38H,#02H
         L1:     MOV     39H,#0FFH
         L2:     DJNZ    39H,L2
                 DJNZ    38H,L1
                 RET
                 END