topic Re: MC9S08GT60 SCI baud rate modulo divisor in 8-bit Microcontrollers

MC9S08GT60 SCI baud rate modulo divisor

cschai — Fri, 09 Feb 2007 05:33:12 GMT

hi,
anyone has MC8S08GT60 SCI baud rate modulo divisor table, register SCIxBDH and SCIxBDL (SBR12BR0)?
i cant find in the data sheet. Freescale should have included it.

Thanks.

Re: MC9S08GT60 SCI baud rate modulo divisor

peg — Fri, 09 Feb 2007 05:47:02 GMT

Hi cschai,

It is easiest to use the spreadsheet in AN2494 for this, helps with all clock related issues as well.

Also you may be able to dig out some old posts by me on achieving "standard" baudrates on these devices.

Re: MC9S08GT60 SCI baud rate modulo divisor

cschai — Fri, 09 Feb 2007 06:29:24 GMT

thanks!
but did AN2494 really tell the SCI baud rate divisor? it just explain the ICG, is it?
i cant find any SCI baud rate divisor table in AN2494 although it did mention about SCI baud rate！

for example:
if my bus freq = 8Mhz
required baud rate = 19200
from baud rate = bus freq / (16*SBR)
thus SBR ~= 26

what is the setting of SBR to get approximate baud rate divisor of 26?

thanks!

Re: MC9S08GT60 SCI baud rate modulo divisor

peg — Fri, 09 Feb 2007 11:18:00 GMT

Hi,

There is no actual table as it is just the raw 13-bit binary value (e.g. 1=1, 2=2 and 3=3 etc). Mostly you just clear the high register and load the divisor into the low one (as it generally fits in one byte).

The associated spreadsheet with the quoted AN will tell you exactly what to load if you plug in all your details.

In your case the 26dec just goes straight into the low byte of the register (with high byte cleared)

Message Edited by peg on 2007-02-0901:23 PM

Re: MC9S08GT60 SCI baud rate modulo divisor

cschai — Fri, 09 Feb 2007 15:04:23 GMT

Peg,

Thanks....