This section provides an example of how to tune VoD Swing in the DP83825. Figure 4-1 shows the DP83825 before VoD Swing tuning. In this example, a device with a nominal RBIAS is measuring a positive and negative VoD at 100Mbps of 1.068 V and -1.116 V, respectively. As the bounds for this speed is having [0.95 V, 1.05 V] and [-1.05 V, -0.95 V], a -8% tune is desired. This tuning brings the VoD to a theoretical 0.98 V and -1.0272 V.

Figure 4-1 Untuned DP83825 100Mbps VoD

To tune the device for -8% swing use the following procedure.

1. Set register 0x30B = 0xC40
2. Set register 0x30C = 0xF
3. Set register 0x30E = Offset_-1.

   1. Read Reg 0x333 = 0x520B. This means that:

      1. A = 10
      2. B = 8
   2. C = 6
   3. D = 5
   4. Offset_-1 = $2048 \times (2\times 5+1)$ = 22528 = 0x5800

After programming each register, the measured VoD on the scope is 0.996 V and -1.008 V. Figure 4-2 shows the output after tuning -8%.

Figure 4-2 Tuned DP83825 100Mbps VoD