E-Tile Transceiver PHY User Guide

ID 683723
Date 9/08/2023
Document Table of Contents
Give Feedback TX Equalizer

The FFE or TX equalization filter has one post-cursor tap, three pre-cursor taps and one main tap (attenuation). The frequency response of the filter is chosen to compensate for the channel impairments such as intersymbol interference (ISI), crosstalk, frequency-dependent losses and reflections. When a signal is transmitted over a channel, the high-frequency components get attenuated. To save power, de-emphasis is used instead of pre-emphasis. This results in a bit stream which is pre-distorted by the equalizer over several bits.

Table 37.  PMA Transmitter Programmable Parameters
Parameter Mode
Attenuation (ATTN) PAM4, NRZ
Post-tap1 (POST) PAM4, NRZ
Pre-tap1 (PRE1) PAM4, NRZ
Pre-tap2 (PRE2) PAM4, NRZ
Pre-tap3 (PRE3) PAM4, NRZ

Refer to the resources linked below to help calculate transmitter equalization.

Details on TX equalization settings for PAM4 and NRZ signals

TX equalization parameters take the following range.

Table 38.  TX Equalization Settings for PAM4 and NRZ Signals
Cursor Rule Step Size
ATTN 0 ≤ ATTN ≤ 26 18.5 mV/step (0.17 dB)
POST -18 ≤ POST ≤ 18

Increment/decrement by 2

18.5 mV/step (0.34 dB)
PRE1 -10 ≤ PRE1 ≤ 10

Increment/decrement by 2

18.5 mV/step (0.34 dB)
PRE2 -15 ≤ PRE2 ≤ 15 9.25 mV/step (0.17 dB)
PRE3 -1 ≤ PRE3 ≤ 1 9.25 mV/step (0.17 dB)
Note: Where ABS is the absolute value, ABS(PRE3) + ABS(PRE2) + ABS(PRE1) + ATTN + ABS(POST) ≤ 32.

For more details on TX equalization programmability, refer to the description for code 0x0015 in the PMA Attribute Codes section.

The ATTN/PRE/POST taps can be dynamically changed via the Avalon® memory-mapped interface.

For more details on PMA attribute support and programming, refer to PMA/PCS Avalon® Memory-Mapped Interface Register Map and PMA Attribute Codes to configure these parameters.