Posted By
gerliczer
on 2014-07-26
11:19:35
|  Re: Exact TED Frequency a for music beginners :-)
Hmm. I don't think these values are quite right. I calculated quite different numbers with the frequency formula TLC derived ages ago. It was somewhere in the late plus/4 mailing list, IIRC.
Anyway, here is the basic program I used to do the math. Feel free to find errors in it.
LIST
10 R=0:I=0
20 D=200000:J=R
30 F=110*(2^(I/12)):IF F>3520 THEN END
40 G=110840.46875/(1024-((R+1)AND1023))
41 REM G=111860.78125/(1024-((R+1)AND1023))
50 IF ABS(G-F) < ABS(D) THEN D=G-F:J=R:ELSE PRINTI;":",F,D,J:I=I+1:GOTO 20
60 R=R+1:IF R<1024 THEN 40
READY.
Line 40 is for the PAL machines, line 41 is obviously for the NTSC ones. And no line for the Drean machines. 
I is an index, R is the register value, F is the frequency of the note we are trying to approximate, G is the generated frequency and D is the variable used to select the smallest difference. If I not screwed up too badly, this code will print those register values that generate frequencies having the smallest difference compared to the desired note frequencies.
Edit: To find the frequency formula open TLC's member page, click the link to his mailing list posts and find post #1550. You can find the formula after the sea of tabulated numbers in the part where he gives advice to emulator writers.
Edit 2: Part of the basic code somehow got interpreted as a kind of html tag and was messed up. I hope this change fixes it.
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