The calculation of index values is described in application note AN-951, which is available here:
http://www.analog.com/static/imported-files/application_notes/AN-951.pdf
On page 11 you can find the formula for converting 28.0 index values to 5.23 values stored in RAM.
Just for everybody's reference, I've listed the first 50 index points in the table below.
| Index | Value (5.23 format) |
| 0 | 0 |
| 1 | 1.19209E-07 |
| 2 | 2.38419E-07 |
| 3 | 3.57628E-07 |
| 4 | 4.76837E-07 |
| 5 | 5.96046E-07 |
| 6 | 7.15256E-07 |
| 7 | 8.34465E-07 |
| 8 | 9.53674E-07 |
| 9 | 1.07288E-06 |
| 10 | 1.19209E-06 |
| 11 | 1.31130E-06 |
| 12 | 1.43051E-06 |
| 13 | 1.54972E-06 |
| 14 | 1.66893E-06 |
| 15 | 1.78814E-06 |
| 16 | 1.90735E-06 |
| 17 | 2.02656E-06 |
| 18 | 2.14577E-06 |
| 19 | 2.26498E-06 |
| 20 | 2.38419E-06 |
| 21 | 2.50340E-06 |
| 22 | 2.62260E-06 |
| 23 | 2.74181E-06 |
| 24 | 2.86102E-06 |
| 25 | 2.98023E-06 |
| 26 | 3.09944E-06 |
| 27 | 3.21865E-06 |
| 28 | 3.33786E-06 |
| 29 | 3.45707E-06 |
| 30 | 3.57628E-06 |
| 31 | 3.69549E-06 |
| 32 | 3.81470E-06 |
| 33 | 3.93391E-06 |
| 34 | 4.05312E-06 |
| 35 | 4.17233E-06 |
| 36 | 4.29153E-06 |
| 37 | 4.41074E-06 |
| 38 | 4.52995E-06 |
| 39 | 4.64916E-06 |
| 40 | 4.76837E-06 |
| 41 | 4.88758E-06 |
| 42 | 5.00679E-06 |
| 43 | 5.12600E-06 |
| 44 | 5.24521E-06 |
| 45 | 5.36442E-06 |
| 46 | 5.48363E-06 |
| 47 | 5.60284E-06 |
| 48 | 5.72205E-06 |
| 49 | 5.84126E-06 |
| 50 | 5.96046E-06 |
This FAQ was generated from the following discussion: How to calculate an RMS table values to select filter curves?