topic Re: Question on bus frequency for S08QD2 family in 8-bit Microcontrollers

Question on bus frequency for S08QD2 family

eyang — Thu, 28 Jul 2011 09:07:18 GMT

I got a trouble while using S08QD2.

I used internal clock source, and all ICS settings as default. The bus frequency should be 8M, but I test a timer with 312us, it's actually about 560us.

Maybe it caused by no calibration ICS, am I right? I wonder if any development tool can do calibration for S08 ICS module? I means if possible to do it via BDM using current development tools(like programmer...)

Thanks a lot!

Re: Question on bus frequency for S08QD2 family

raining — Thu, 28 Jul 2011 13:03:32 GMT

Recommended USBDM, you can correct ICS, focus is cheap, and calibration accuracy is quite high.

Re: Question on bus frequency for S08QD2 family

eyang — Thu, 28 Jul 2011 16:13:03 GMT

You mean USBDM tool can do calibration via PC? Would you please advise me more detail about calibration process.

If I can buy this tools in China?

Thanks！

Re: Question on bus frequency for S08QD2 family

raining — Thu, 28 Jul 2011 16:28:13 GMT

You can look at the seller's demo movie, which use the standalone programmer, just fill in the required frequency, to download.

Re: Question on bus frequency for S08QD2 family

bigmac — Thu, 28 Jul 2011 22:02:47 GMT

Hello, and welcome to the forum.

The maximum untrimmed frequency range for the internal reference is 25-41.66kHz, with a central value of 31.25kHz. This is for an ICSTRM setting of 0x80. The central value corresponds with a maximum bus frequency of 8MHz. Depending on the ICSC2_BDIV setting, the bus frequency may be reduced to 4MHz, 2MHz or 1MHz nominal. The power-up default setting is for a trimmed bus frequency of 4MHz. You will need to alter the BDIV setting to achieve 8MHz bus frequency. I wonder is this is part of the problem, since the frequency error seems to be too great for the trim setting alone.

Check the value within the ICSTRM register. A value of 0x80 represents the power-up default setting. A value of 0xFF would indicate that the setting has been updated from flash memory (address 0xFFAF), to reflect the non-volatile trim setting, but this location has been erased, and no longer holds the factory trim setting.

What flash programming tools are you using? CodeWarrior debug mode, in conjunction with P&E USB Multilink BDM interface, certainly is capable calibrating the non-volatile trim settings, at addresses 0xFFAE and 0xFFAF, during the normal programming process. But your code will need to transfer these settings to their respective registers, for trimming to occur. This must be done prior to any change of the BDIV setting, so that the maximum allowable bus frequency is never exceeded.

Regards,

Mac