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Re: CYGNUM_HAL_RTC_PERIOD
- From: Chuck McManis <cmcmanis at mcmanis dot com>
- To: "vasantha.rajan" <vasantha dot rajan at cranessoftware dot com>,
- Cc: ecos-discuss at ecos dot sourceware dot org
- Date: Fri, 17 Feb 2006 14:17:35 -0800
- Subject: Re: [ECOS] CYGNUM_HAL_RTC_PERIOD
- References: <200602171910.56724.vasantha.rajan@cranessoftware.com>
At 05:40 AM 2/17/2006, vasantha.rajan wrote:
I have some doubt in CYGNUM_HAL_RTC_PERIOD. I will list my doubts
1. In my code I just want to trigger my alarm for some micro seconds (say for
25 us)
That is a very short time for most systems. Yours especially.
Ignoring other aspects (like how the RTC timer is configured) for the
moment, realize that on average the ARM9 achieves about 1.5 cycles per
instruction. (This from the ARM9 FAQ) and that when clocked at 150Mhz
(which the Excalibur board apparently is) that's roughly 100 million
instructions per section. So 25 micro seconds is roughly 2500 instructions.
At 3 instructions per line of C code (on average) that's about 833 lines of
C code between clock ticks.
Perhaps you need some specialized hardware to meet this timing requirement?
--Chuck
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