> Where are you getting the +31 from? Is this in the User's Manual? No in user's manual. The +31 is rounding up purpose.
> Computations are for mathematicians. Real engineers measure the actual frequency. ;-) Agree. > If you change the " - 31" to " - 42", your computations will result in a different divisor. > Why are you subtracting what appears to be an arbitrary number (31)? Can't use 42 when the user's manual spec the divisor is 32. The "- 31" comes from counter = ((bus_freq / baudrate) + 31) / 32. Using the same calculation as mentioned here to find out bus_freq. bus_freq = ((counter * 32) - 31) * baudrate. > Are you sure your input frequency is 140MHz and not 144MHZ??? Have you read the itty-bitty > numbers on the crystal? Have you put a scope on it and actually measured it? Never trust > those hardware people. ;-) Actually, the bus freq is 70Mhz, 140Mhz is cpu freq (scope measurement). The input freq (crystal/oscillator) not always 1 to 1 ratio. Take M5253EVBE for example, the input clk is 11Mhz. Then, it multiply up and divide down for CPU and bus frequency. > Looking at the MFC5407 (arbitrarily, not knowing what processor you have), the dividers are > as expected and *do not* match your "- 31" > calculations. They have a simple example and simple math that matches (no "- 31"). > Hmmm, the MFC5407 has a max CLKIN (and thus bus clock) of 54MHz. You must have a different > flavor. MFC548x maxes at 50MHz. > What processor are you using? 52x2, 532x, 547x_8x, 5445x. The 5253EVB is having the issue where the calculation does not apply if baudrate is 115200. > Ahh, MFC5249 has a 140MHz bus. Still is a straight forward divide-by n*32, no "- 31". I thought the same too, but the 140Mhz is cpu freq. Regards, TsiChung ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ U-Boot-Users mailing list U-Boot-Users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/u-boot-users