topic Re: MC9S12E64 baudrate value in S12 / MagniV Microcontrollers

MC9S12E64 baudrate value

JohnDoe — Wed, 12 Aug 2009 22:35:00 GMT

Hello

A couple of questions:

Is 115200bps baurate is supported for MC9S12E64? I'm using a 29.4912mhz crystal freq. the calculated divisor is 8. No PLL.

What's the minimum baudrate divisor for SCI?

Thanks

Re: MC9S12E64 baudrate value

WadeH — Thu, 13 Aug 2009 22:18:10 GMT

The Reference Manual says:

"The value from 0 to 8191 written to the SBR12–SBR0 bits determines the module clock
divisor.

SCI baud rate = SCI module clock / (16 * SCIBR[12:0]) "

.. which seems to say that 115.2kBd is achievable. And, in the case of a 29.412MHz clock,

the baud-rate error is 0%:

115,200 = (29.4912e6/2) /(16 * D) ===> D= 8.000

For a 25MHz clock, the nearest baud-rate to 115.2k is

(25e6/2 )/(16*7) = 111.6kBd... which is slow by about 3%, but works flawlessly

(for desktop debug distances, anyway) on my ne64 boards

Re: MC9S12E64 baudrate value

JohnDoe — Thu, 13 Aug 2009 22:27:44 GMT

Thank you Wade. So the answer is yes. I was asking this because some microcontrollers limit they baudrate by 0.x rate of the frequency bus, and I didn't find any other restriction on the Manual.

John