CS2300-CP

DS843F1

29

9. CALCULATING THE USER DEFINED RATIO

Note:

The software for use with the evaluation kit has built in tools to aid in calculating and converting the User

Defined Ratio. This section is for those who are not interested in the software or who are developing their

systems without the aid of the evaluation kit.

Most calculators do not interpret the fixed point binary representation which the CS2300 uses to define the output

to input clock ratio (see Section 5.3.1 on page 16); However, with a simple conversion we can use these tools to

generate a binary or hex value which can be written to the Ratio register.

9.1

High Resolution 12.20 Format

scaled decimal representation; then use the decimal to binary/hex conversion function on a calculator and

write to the register. A few examples have been provided in Table 2.

Table 2. Example 12.20 R-Values

9.2

High Multiplication 20.12 Format

scaled decimal representation; then use the decimal to binary/hex conversion function on a calculator and

write to the register. A few examples have been provided in Table 3.

Table 3. Example 20.12 R-Values

Desired Output to Input Clock Ratio

(output clock/input clock)

Scaled Decimal

Representation =

(output clock/input clock)

Hex Representation of

12.288 MHz/10 MHz=1.2288

1288490

00 13 A9 2A

11.2896 MHz/44.1 kHz=256

268435456

10 00 00 00

Desired Output to Input Clock Ratio

(output clock/input clock)

Scaled Decimal

Representation =

(output clock/input clock)

Hex Representation of

12.288 MHz/60 Hz=204,800

838860800

32 00 00 00

11.2896 MHz/59.97 Hz =188254.127...

771088904

2D F5 E2 08