Mathematics and remainder for PLL MC145158

**RFsolution** · - 16th August 2005, 20:03

Hi All

I need some help with some mathematics and remainders, which might not be that difficult if you know how to handle it

Here is what I want to do and calculate in pbp:

I want to determine the A and N counters from a dual modulus PLL MC145158 for who might be familiar with it, if not:
I receive with serin a value which is 6 digits with 1 decimal point a frequency in Khz with 1 decimal
ex: 433687,5 which is Freq as variable or if easyer 433 (in one variable) , and 6875 in another

So:

Freq = var ??? (because it is bigger than 16bit

I have 3 variable, one is fixed which needs to be calculated as followed:

R = var word (14bit)
R = 800 '(fix value untill now)
N = var word (10bit) 'to be calculated
A = var word (7bit) 'to be calculated
temp var word

here is what I need to do in PBP comming from a original C source:

unsigned long temp,nlong,along
Temp = (501800 - 433687,5) * 800
Nlong = temp/64000
Along = (temp-(Nlong*64000))/1000
N = (unsigned int) Nlong
A= (unsigned int)Along

example: freq is 433,6875 Mhz
temp = (501800 - 433687,5) * 800 = 54490000
Nlong = temp/64000 = 54490000/64000 = 851,40625000 (64000 is a fixed divider ratio)
Along = ((Nlong*64000))/1000 = (0,406250*64000))/1000 = 26 '0,406250 is remainder from 851,406250

result should be:
N = 851 without remainder
A = 26

Anyone who can help me

**Darrel Taylor** · - 17th August 2005, 20:25

HI RFsolution,

I was trying to work thru this calculation, but I have a question. There's seems to be 2 different ways of calculating "Along".

In the "here is what I need to do " section, it's...
Along = (temp-(Nlong*64000))/1000

Then in the example, it's
Along = ((Nlong*64000))/1000

For now, I'm assuming the second one is correct, but just wanted to verify it with you.<br><br>

**Darrel Taylor** · - 18th August 2005, 06:56

Well, nevermind, I got it figured out anyway.

Give this a try.

Code:

<font color="#000000"><b>Freq1      </b><font color="#008000"><b>VAR WORD
</b></font><b>Freq2      </b><font color="#008000"><b>VAR WORD

</b></font><b>N          </b><font color="#008000"><b>VAR WORD
</b></font><b>A          </b><font color="#008000"><b>VAR WORD
</b></font><b>Remainder  </b><font color="#008000"><b>VAR WORD


</b></font><font color="#0000FF"><b><i>; --- Frequency must be split into 2 variables ---
</i></b></font><b>Freq1 </b>= <b>4336   </b><font color="#0000FF"><b><i>; 433687.5
</i></b></font><b>Freq2 </b>= <b>875
</b><font color="#008000"><b>GOSUB </b></font><b>PLL_Calc

</b><font color="#008000"><b>STOP

</b></font><b>PLL_Calc</b>:
    <b>N </b>= (<b>5018 </b>- <b>Freq1</b>)     
    <font color="#008000"><b>IF </b></font><b>Freq2 </b>&gt; <b>0 </b><font 

color="#008000"><b>THEN          
        </b></font><b>A </b>= <b>1000 </b>- <b>Freq2   
        N </b>= <b>N </b>- <b>1      
    </b><font color="#008000"><b>ELSE                       
        </b></font><b>A </b>= <b>0              
    </b><font color="#008000"><b>ENDIF                      
    </b></font><b>N </b>= <b>N </b>* <b>8          
    A </b>= <b>A </b>* <b>8          

    N </b>= <b>N </b>+ (<b>A</b>/<b>1000</b>)       
    <b>A </b>= <b>A </b>- (<b>A</b>/<b>1000</b>*<b>1000</b>)  
        
    <b>N </b>= <b>N</b>*<b>10                   
    N </b>= <font color="#008000"><b>DIV32 </b></font><b>64                   
    Remainder </b>= <b>R2                     
    Remainder </b>= <b>Remainder </b>* <b>10000      
    Remainder </b>= <font color="#008000"><b>DIV32 </b></font><b>64               
    
    A </b>= <b>A </b>* <b>10000              
    A </b>= <font color="#008000"><b>DIV32 </b></font><b>64                   
    
    A </b>= <b>A </b>+ <b>Remainder
    A </b>= <b>A </b>* <b>64
    A </b>= <font color="#008000"><b>DIV32 </b></font><b>10000
    Remainder </b>= <b>R2
    </b><font color="#008000"><b>IF </b></font><b>Remainder </b>&gt;= <b>5000 </b><font 

color="#008000"><b>THEN </b></font><b>A </b>= <b>A </b>+ <b>1
</b><font color="#008000"><b>RETURN</b></font>

**RFsolution** · - 21st August 2005, 16:24

Hi darrel

I gave it a try but I think there is still a problem

As I told you it is a part of the C routine, but if i take the remainder from
:
Nlong = temp/64000 = 54490000/64000 = 851,40625000
so the remainder is 0,40625000 and multiply by 64000 divide by 1000
is giving me the correct A value

Tis is not the case with your example

Can you have a look ?, you can try any example of freq (in the range 430000.0 til 440000.0 following my example

Thanks again

**Darrel Taylor** · - 21st August 2005, 19:33

OOPS, you're right.

Somehow, in the process of posting it, I lost two 0's in the third DIV32.

This works better.

Code:

<font color="#000000"><b>Freq1      </b><font color="#008000"><b>VAR WORD
</b></font><b>Freq2      </b><font color="#008000"><b>VAR WORD

</b></font><b>N          </b><font color="#008000"><b>VAR WORD
</b></font><b>A          </b><font color="#008000"><b>VAR WORD
</b></font><b>Remainder  </b><font color="#008000"><b>VAR WORD


</b></font><font color="#0000FF"><b><i>; --- Frequency must be split into 2 variables ---
</i></b></font><b>Freq1 </b>= <b>4336   </b><font color="#0000FF"><b><i>; 433687.5
</i></b></font><b>Freq2 </b>= <b>875
</b><font color="#008000"><b>GOSUB </b></font><b>PLL_Calc

</b><font color="#008000"><b>STOP

</b></font><b>PLL_Calc</b>:
    <b>N </b>= (<b>5018 </b>- <b>Freq1</b>)     
    <font color="#008000"><b>IF </b></font><b>Freq2 </b>&gt; <b>0 </b><font 

color="#008000"><b>THEN          
        </b></font><b>A </b>= <b>1000 </b>- <b>Freq2   
        N </b>= <b>N </b>- <b>1      
    </b><font color="#008000"><b>ELSE                       
        </b></font><b>A </b>= <b>0              
    </b><font color="#008000"><b>ENDIF                      
    </b></font><b>N </b>= <b>N </b>* <b>8          
    A </b>= <b>A </b>* <b>8          

    N </b>= <b>N </b>+ (<b>A</b>/<b>1000</b>)       
    <b>A </b>= <b>A </b>- (<b>A</b>/<b>1000</b>*<b>1000</b>)  
        
    <b>N </b>= <b>N</b>*<b>10                   
    N </b>= <font color="#008000"><b>DIV32 </b></font><b>64                   
    Remainder </b>= <b>R2                     
    Remainder </b>= <b>Remainder </b>* <b>10000      
    Remainder </b>= <font color="#008000"><b>DIV32 </b></font><b>64               
    
    A </b>= <b>A </b>* <b>10000              
    A </b>= <font color="#008000"><b>DIV32 </b></font><b>6400       <font color="#0000FF">; <-- Changed, was 64</font>           
    
    A </b>= <b>A </b>+ <b>Remainder
    A </b>= <b>A </b>* <b>64
    A </b>= <font color="#008000"><b>DIV32 </b></font><b>10000
    Remainder </b>= <b>R2
    </b><font color="#008000"><b>IF </b></font><b>Remainder </b>&gt;= <b>5000 </b><font 

color="#008000"><b>THEN </b></font><b>A </b>= <b>A </b>+ <b>1
</b><font color="#008000"><b>RETURN</b></font>

**RFsolution** · - 22nd August 2005, 10:09

Sorry Darrel, can you have a look again ?
In the code A = (A/1000*1000) does not do anything
So the A counter value is not calculated correctly

Is it possible to use for freq1 only the 3 first digits
for freq2 4 digits, it makes more sense and easyer for the serin2 command
to enter the completer frequency

433.6875 Mhz so we can split 433 and 6875 into 2 variables

What you think ?

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