8-bit MicrocontrollersのトピックRe: Suggest for use MC9S08SH8

Suggest for use MC9S08SH8

rtribaudino — Thu, 29 Nov 2007 02:25:41 GMT

It's the first time that I Write on this forum.

I'm just working with S08SH and I'will use SCI to 19200 baud, with external crystal 16MHz.

I desire to have freq. of busclock to work 8MHz, but working with 16MHz crystal is necessary to set cpu in FBELP mode. In this mode BDC is not enable and i cannot debug the application.

Do you have some suggest to obtain 19200 baud with 8MHz of bus clock with or not External crystal?

Naturally i need to use BDC module.

Thank you very much for yours suggests

Riccardo

Re: Suggest for use MC9S08SH8

Ake — Thu, 29 Nov 2007 17:41:01 GMT

Hi,

You should be able to run the BDM, no matter which baud rate you have set up for the SCI or which external clock you are using.

I have no experience with the 9S08SH8, but as the SCI module is the same is all other 9S08s, this should to the trick.

If you have an 8 MHz bus clock and want to run the SCI at 19.2 kBaud, the SCI receiver must run 16 times faster, or 16 * 19.2 Kb = 307.2 kHz.

If you divide 8 MHz/307.2 kHz = 26.04.

So set the

SCIBD = 26;

and it ought to do the trick.

Regards,

Ake

Re: Suggest for use MC9S08SH8

rtribaudino — Thu, 29 Nov 2007 21:42:06 GMT

Thank you Ake

The SCI module is identical to other MCS08, but the source clock for this cpu is different. So actually I cannot use 16Mhz of crystal because the clock for BDC module is not provided.

I'm not understand how i can run the bus clock to 8 MHz with a crystal of 16Mhz in FBE mode or in other mode in the way that i can use the BDC clock for debugging.

Regards

Riccardo

Re: Suggest for use MC9S08SH8

Ake — Thu, 29 Nov 2007 22:33:02 GMT

Hi,

I have no DEMO9S08SH8 MCU, so I will have to read the manual and guess.

So here are my guesses:

1) If you want to run with an external crystal, the FLL should run in a Bypassed External (FBE) mode.

The BDM is active in this mode

But there really was a lot of the BDM in the 9S08SH8 manual.

I would like to have some hardware to play with to get a good understanding about it.

Sorry about that!

Regards,

Ake

Re: Suggest for use MC9S08SH8

rtribaudino — Fri, 30 Nov 2007 00:36:13 GMT

Hi,

now a read the manual , but it's not very clear. I don't understand if the BDC can use ICSCLK or BUS CLOCK. So if i work with 16Mhz crystal i need to go in FBELP mode. At this point the ICSLCLK is not avaible(pag 153 of the manual). I don't understand if BDC can use the bus clock. The manual is not clear about that.

I will try on my board, but if someone has some idea i will appreciate it.

Thank you

Riccardo

Re: Suggest for use MC9S08SH8

rtribaudino — Fri, 30 Nov 2007 01:49:55 GMT

Hi,

everything it's ok. The BDC clock can be Busclock in FBELP mode.

The problem is my development tool (better I was the problem). I've used for BDC clock the fixed clock in the setting of tool. The better way is to use Busclock for BDC.

Thanks

Riccardo

Re: Suggest for use MC9S08SH8

han_lin — Fri, 01 Feb 2008 09:53:00 GMT

Hi,

Have you considered using internal source clock in your application as well? You can also generate 8 MHZ bus with the built-in internal source clock. It has a +/- 2 % accuracy. That way you can save some board space use for external crystal.

Han