HCS12XDT512 & PLL stability

[Eric_t]

Hi!

I am using HCS12XDT512 with 16MHz crystal and PLL filter. The desired frequency for cpu bus is 14.7MHz.

I have used processor expert to calculate the correct values for SYNR & REFDV.

Processor expert gives SYNR=0x2E and REFDV=0x32.

I have used the S12X PLL filter calculator Beta 2 to check PLL stability.

The problem is that S12X PLL filter calculator, shows that maximum REFDV value is 15 (S12X PLL filter calculator says that the processor expert calculated value is wrong)

I suppose that the processor expert gives correct results and the problem is at S12X PLL filter calculator.

Does anyone know if there is a newer version of S12X PLL filter calculator?

I have attached a picture.

[dianabatrlova]

Hi Eric,

You are using the calculator which is intended for the HCS12 devices such as MC9S12DP256.

This kind of MCUs have REFDIV[3:0]. The range is 0 - 15. So, you can set the maximum value of REFDIV = 15.  

The S12XDT512 MCU has REFDV[5:0] and the range is 0 - 63.

The Processor Expert give you correct results and the PLL calculator is not determined for the S12XDT512 MCU.

Best regards,

Diana