Doubt in SIC bit using on-chip I2C of LPC2148

Thank You very much. One more doubt regarding RTC. Let as assume we have 12MHz crystal oscillator, which is divided by 12 to get 1MHz oscillator frequency. This clock may produce 1sec delay accurately which can be used for time display instead of RTC?

If not, can you tell me the significance of RTC and separate crystal(32.678KHz) for 1 sec delay.

You should be able to use whatever timers/clocks you want to mark time. People often use timers (SysTick) to generate 1 ms (1KHz) interrupts, and mark time off that way. These timers tend to require that the processor is running, and consume more power. Low frequency clocks like the 32.768 KHz tend to be run in low power portions of the design, and in backup power domains. This would allow the processor to stop, while the RTC keeps ticking, and it can waken the processor on second or alarm intervals.

Besides being able to turn off all main clocking and still have the RTC running with the 32.768kHz crystal, that lower frequency crystal also has the advantage that it is more stable - a crystal running at that low frequency is larger and heavier than a 12MHz crystal which makes it less affected by contamination inside the crystal casing.

Thank you very much. I have understood the significance of RTC. I have started learning LPC2148 and making use of on-chip peripherals. Started using parallel ports,on-chip I2C module and I like to use on-chip USB port.At present I am looking up the data sheet. It seems difficult.It would be better if I know the steps to learn USB, on-chip USB module, understanding registers related to it, etc.,. Kindly help me in this regard.

Really I am happy to clear all my doubts in one day through this forum. Thank your very much for this wonderful opportunity. Expecting the same support forever.