设单片机晶振频率为12MHZ，试编写一延时1s的子程序

DELAY1S: MOV R2,#10 DLY1: MOV R3,#200 DLY2: MOV R4,#248 DJNZ R4,$ DJNZ R3,DLY2 DJNZ R2,DLY1 RET