18.104.22.168. Purpose of PMA Tuning
You can see the value of PMA tuning by considering the following two cases:
- Case 1—Optimum link performance measured by executing initial adaptation at static (minimum and maximum) temperatures
- Case 2—Optimum link performance for a temperature sweep (real time dynamic temperature condition) may not be achieved with initial adaptation and continuous adaptation.
The temperature is increased with continuous adaptation running in the background. Continuous adaptation is required in dynamic temperature conditions and its adaptive range is highly dependent on initial adaptation conditions. The goal of continuous adaptation is to compensate for temperature changes and ensure the link performance is as near as possible to the initial adaptation performed at the low temperature in Case 2. As the temperature increases, the eye degrades at the sampler and reports a relatively higher BER. Continuous adaptation started at a lower temperature does not result in the optimal performance observed at a higher static temperature in Case 1 after running initial adaptation. This implies that continuous adaptation is unable to maintain the performance obtained after running initial adaptation.
You can reduce this link performance degradation between the static temperature (Case 1) and dynamic temperature (Case 2) conditions by tuning the PMA AFE parameters. This establishes the desired dynamic temperature performance of continuous adaptation close to the initial adaptation at high temperature.
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