[En-Nut-Discussion] Serial Baudrate of 1Mb by the Ethernut3

Harald Kipp harald.kipp at egnite.de
Tue Jul 25 17:37:04 CEST 2006

Hi Michael,

Thanks for jumping in. However, Martin was referring to Ethernut 3,
which provides a programmable PLL. Thus, there's no need to change
the crystal.

There are two options.

- Change PLL output Clock C to a different frequency.
Unfortunately I can't find the sample I created some weeks
ago, which demonstrated how to modify the CPU clock.
This link may help:

- Route one of the PLL clocks through the CPLD to the
UART clock input. This way only the externally clocked
UART will run at 1 MBaud and the remaining UARTs can still
provide standard baudrates.

Two things to be aware of

1. The AT91R40008 is 3.3V and is not(!) 5V tolerant. The CPLD
is 5V tolerant.

2. Changing to clocks to bad values may destroy the board.
Carefully check your settings twice.


At 15:22 25.07.2006 +0200, you wrote:

>You will have to change the crystal from 14.745MHz to 16MHz...
>-----Original Message-----
>How can i adjust the baud rate mor or less exactly to 1'000'000? Must i
>change the CPU clock frequency of the Ethernut3 or can i change the baud
>rate more exactly with an other solution?
>Martin Anrig

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