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I figure you are using a 8051 variant? The maximum delay produced by a single timer in 8051 is 71ms approx.Thats for mode 1. But you are using mode 2 which can have a maximum delay of approx .277 ms or something like that. You can use a counter to repeat this again and again but that would be too large. Other wise you get a 60 HZ clock pulse from a 555 timer. Program the counter in the 8051 to count 60 pulses(use autoreload mode) since you will repeat it for five seconds(counter). And then do what ever you want.If you want to ask anything else then ask away.