The 1024 Hz interrupt obtained this way is synchronous with the times that the RTC seconds and other counters change. You are also assured that you will get exactly 1024 interrupts per second as tracked by the RTC chip. (Now, if the seconds tracked by the RTC chip are truly real seconds is another subject for a different forum thread on calibration).

If you use the 8051 T1 or T2 timer interrupts to get the millisecond level timing then, since it is on a different crystal timebase than the RTC, there is NO guarantee the interrupts from the timers will be synchronized with the timing changes in the RTC chip and that the interrpts after 1024 of them will not have accumulated the same "second" that the RTC chip does.

Now of course if you don't give a hoot about this synchronization and same frequency base thing then by all means go ahead and use the timer resources on board the procesor.
Michael Karas


Thanks
Michael Karas