hi folks
here is somthing interesting i am using at89c52.
in interrupt service routine i used to stop timer like this
inerrupt0_isr:
clr tcon.4
mov th0,#new_msb
mov tl0,#new_lsb
setb tcon.4
reti

isr_timer0:
cpl port3.1
clr tcon.4
mov th0,#new_msb
mov tl0,#new_lsb
setb tcon.4
reti
timer0 is loaded every time with an interrupt,some time it get stoped in intr0
routine with clr tcon.4,sometime not what is the reason


how i came to know timer get stoped or not
see the cycle starts with interrupt like this

intr--->timer stoped(with clr tcon.4 it was generating square pulse)----->timer reloaded by delay----->in timer isr timer reladed with duty cycle of square pulse(after delay is over)------->intr

now as the intr arrive square pulse should stop and delay should be executed,there should be no pulse in delay time but it is when i see on cro although it is not countinuose it flicker some time in delay time.
i had wasted 5 day on this partcular problem
one more interesting obsevation which i like to share my interrupt time is 10 millisecond this mean whole cycle
intr---->delay---->square pulse
cannot be more than 10ms,after 10 ms square pulse had to stop what i had done to stop the square pulse forcefully i start another timer for 10ms in parallel witn intr0 it is used to stop timer generating square now every thing work well but i am wasting one time more not good practice