5位十进制计数器

;FOR    EAT598
;---------------------------------------------------------
C8255   EQU     0F22BH          ;8255命令口地址
P8255A  EQU     0F228H          ;8255 PA口地址
P8255B  EQU     0F229H          ;8255 PB口地址
P8255C  EQU     0F22AH          ;8255 PC口地址
KEYVAL  EQU     30H            ;读到的键码
;---------------------------------------------------------
        ORG     0000H
        SJMP    START
        ORG     000BH
        RETI
        ORG     001BH
        ;AJMP    INT_T1
        ORG     0030H
START:        
        MOV     SP,#60H
        LCALL   DELAY  
        MOV     TMOD ,#05H
        MOV     TL0,#00H
        MOV     TH0,#00H
        MOV     TL1,#00H
        MOV     TH1,#4BH
       ; MOV     R2,#10
        MOV     KEYVAL,#00H     ;置显示初始值
        MOV     DPTR,#C8255
        MOV     A,#82H          ;PB口输入,PA,PC口输出
        MOVX    @DPTR,A
        MOV     DPTR,#P8255C    
    MOV     A,#00H

    MOVX    @DPTR,A
    MOV     32H,#00H
    MOV     33H,#00H
    MOV     34H,#00H
    MOV     35H,#00H
            MOV     36H,#00H 
   ; SETB    TR1
    SETB    ET0
    ;SETB    ET1
    SETB    EA
       ;MOV     R3,#145
KB_DIS:
        LCALL   RD_KB          ;读键子程序
        MOV     R7,KEYVAL 
        CJNE    R7,#10,FLAG1
        SETB    TR0
FLAG1:  CJNE    R7,#13,FLAGZS
        CLR     TR0   
FLAGZS: CJNE    R7,#12,FLAG2
           
FLAG2:   
        CJNE    R7,#12,FLAG3
    MOV     32H,#00H
    MOV     33H,#00H
    MOV     34H,#00H
    MOV     35H,#00H
            MOV     36H,#00H
    MOV     TL0,#00H
FLAG3:     
        CJNE    R7,#14,FLAG4