ULN2003A输出怎么老是低电压啊

ORG 0030H

MAIN:
MOV R0,#1

LOOP2: MOV R2,#01H
MOV R6,#200
MOV R7,#6

LOOP1:
MOV DPTR,#STU1
MOV A,R0
MOVC A,@A+DPTR
ANL A,#0FH
MOV DPTR,#SEG
MOVC A,@A+DPTR
MOV P2,R2
MOV P1,A
LCALL DELAY1
MOV A,R2
RL A
MOV R2,A
INC R0
DJNZ R7,LOOP1
DJNZ R6,LOOP2
MOV P2,#0
LCALL DELAY2

LOOP4: MOV R2,#01H
MOV R6,#200
MOV R7,#6

LOOP3:
MOV DPTR,#STU1
MOV A,R0
MOVC A,@A+DPTR
ANL A,#0FH
MOV DPTR,#SEG
MOVC A,@A+DPTR
MOV P2,R2
MOV P1,A
LCALL DELAY1
MOV A,R2
RL A
MOV R2,A
INC R0
DJNZ R7,LOOP3
DJNZ R6,LOOP4
MOV P2,#0
LCALL DELAY2
LJMP MAIN
DELAY1:
MOV 08H,#2
DY2: MOV 09H,#230
DY1: DJNZ 09H,DY1
DJNZ 08H,DY2
RET

DELAY2:
MOV 0AH,#125
DY5: MOV 0BH,#2
DY4: MOV 0CH,#230
DY3: DJNZ 0CH,DY3
DJNZ 0BH,DY4
DJNZ 0AH,DY5
RET

SEG:
DB 3FH,06H,5BH,4FH,66H,6DH,7DH,07H,7FH,6FH

STU1:
DB "108124"

STU2:
DB "108118"

END

我的程序是这样的，目的是让数码管显示108124，过会再显示108118，但是问题是ULN2003A反向器输出端却总是低电压，怎么回事？要如何解决呢？？？