MC9S12C64MFA PLL XFC component calculation question

[roberthiebert]

I want to use the 48 LQFP version of the MC9S12C64MFA micro controller in a new project, but I don't have enough knowledge to calculate the values for the phase lock loop filter components RS, CS and CP. I want to use an 8mHz Pierce oscillator and have a 24mHz bus speed. If anyone could do the calculations and provide me with the values I'd really appreciate it.

Thanks

Robert

[roberthiebert]

Thank you very much. That should be what I need, but are you sure it applies to the MC9S12C64MFA?

Regards,

Robert

[lama]

Hi,

Yes, this one "HCS12 PLL Filter.exe" is for 250nm technology devices like 9S12C.

Best regards,

Ladislav

[roberthiebert]

Hi Ladislav,

I must be doing something wrong. If I use S12XE_iPLL_Calc103 and plug in OSC = 8 mHz, Bus Freq = 24 mHz it gives me a SYNR of 0X02 and a REFDV of 0X80.

When I use HCS12PLL Filter and plug in Osc Freq= 24mHz and a SYNR = 2 so far so good. But when I try to plug in REFDV = 80 I get a dialog box stating max REFDV is 15. What am I doing wrong?

Regards,

Robert 

[lama]

Hi,

do not use XE_iPLL calculator. It is for 180nm technology devices of family S12XE.

As I wrote HCS12PLL Filter is the right for you....standard S12D,C,A,... 250nm technology devices.

Best regards,

Ladislav

[roberthiebert]

Hi Ladislav,

Thanks for the confirmation.

If I use the calculator with OSC frequency = 8mHz, a RFDV = 0 and SYNR = 2 it results in a 24mHZ bus speed, which is what I want. The medium stability calculator with 5% resistors give me an RS = 5.1K, Cs = 2.2nF (0.0022uF) and CP = 0.22nF (220pF).

I have a working circuit with the same OSC frequency and SYNR and RFDV values. It uses an RS of 3.9K, CS = 0.0033uF (3.3nF) and CP = 330pF (.33nF). Will this result in slightly higher stability with a slightly longer lock time than the calculator values?

Regards,

Robert

Robert  

[lama]

Hi,

These are all combinations you can use in S12(X) family.

SYNR =2[0x00]; REFDV=0[0x00]

SYNR =11[0x0B]; REFDV=3[0x03]

SYNR =14[0x0E]; REFDV=4[0x04]

SYNR =17[0x11]; REFDV=5[0x05]

SYNR =20[0x14]; REFDV=6[0x06]

SYNR =23[0x17]; REFDV=7[0x07]

The combination SYNR =0[0x00]; REFDV=2[0x02] provides the best lock time result.

We have investigated in past that the circuit is relatively robust and works also with different Rs, Cs, Cp. Your parameters are close to calculated. However, there is no study of influence of change of these parameters wit SYNR=const, REFDV=const. … and we do not see to the code of the application.

I see the parts you use are not any problem.

Best regards,

Ladislav

[roberthiebert · Accepted solution]

Hi Ladislav,

Thanks so much for taking the time to answer my questions. Now I can go ahead and build the circuit with confidence.

Regards,

Robert

[lama]

Hi,

Download a calculator from:

https://community.nxp.com/t5/S12-MagniV-Microcontrollers/S12X-PLL-Filter-Calculator/ta-p/1125313

and to get synr and refdv you can use attached PLL FREQUENCY SETUP-S12X-v5_0.xls

Best regards,

Ladislav