can anyone help

for_rise_on1        clr mot1for       ;on period of pwm
                    mov r2,30H
                    djnz r2,$        
                    setb mot1for        ;off period of pwm
                    mov r2,31H
                    djnz r2,$
                    djnz r3,for_rise_on1   ;repeat the loop 10 times     
                    mov r3,#10
                    mov a,30H
                    add a,# 5          ;increment on period by 10 microsec
                    mov 30H,a
                    mov a,31H
                    subb a,# 5         ;decrement off period by 10 microsec
                    mov 31H,a
                    djnz r4,for_rise_on1   ;repeat the loop 20 times     
                    mov r4,#20
                    clr mot1for