我是刚学单片机不久的菜鸟，在做一个例子时出了问题，还望高手指点，谢谢,用的是keil
ORG 0000H
LJMP START
ORG 0030H
START:
CLR P0.4                               5
ACALL DELAY
SETB P0.4                             7
ACALL DELAY
AJMP START
DELAY:
MOV R7,#255
Y1:
MOV R6,#255
DJNZ R6,$
DJNZ R7,Y1
RET
END

可总是在引脚处报错
BASS.ASM(5): error A45: UNDEFINED SYMBOL
BASS.ASM(7): error A45: UNDEFINED SYMBOL

用的芯片是philips 的P89C669