MOV R0,#101
DELAY2:        
        MOV R1,#101
DELAY1:
        MOV R3,#101
        DJNZ R3,$ 
        DJNZ R1,DELAY1 
        DJNZ R0,DELAY2
        CPL P1.0
        RET

I didn't check if it will produce 1 sec delay. But just checked the program.

I would use another approach, to use a timer for a 50 msec interrupt and in the ISR, use a counter to count upto 20 times and then do what ever is desired.