I dunno how to program this timer. I have a ATMEL T89C51RD2 Microcontroller have 2 mode for internal timing (1)40Mhz for standard mode(default) (2)and 20Mhz in X2 Mode. However, I am using a 16Mhz as an exertnal frequency. Problem (1)I need to program a one second timer. How to do it???? Help!!