L- and H-Tile Transceiver PHY User Guide

ID 683621
Date 1/30/2024
Document Table of Contents

3.9.2. PMA and PCS Bonding

PMA and PCS bonding reduces skew between both the PMA and PCS outputs within a group of channels.

For PMA bonding, either x6 or x24 is used. For PMA and PCS bonding, some of the PCS control signals within the bonded group are skew aligned using dedicated hardware inside the PCS.

Figure 163. PMA and PCS Bonding

PMA and PCS bonding use master and slave channels. One PCS channel in the bonded group is selected as the master channel and all others are slave channels. To ensure that all channels start transmitting data at the same time and in the same state, the master channel generates a start condition. This condition is transmitted to all slave channels. The signal distribution of this start condition incurs a two parallel clock cycle delay. Because this signal travels sequentially through each PCS channel, this delay is added per channel. The start condition used by each slave channel is delay compensated based on the slave channel's distance from the master channel. This results in all channels starting on the same clock cycle.

The transceiver PHY IP automatically selects the center channel to be the master PCS channel. This minimizes the total starting delay for the bonded group.
Note: Use the tx_clkout from the master channel as the source clock to drive the tx_coreclkin port for all other channels in the bonded interface.
Note: Because the PMA and PCS bonding signals travel through each PCS block, the PMA and PCS bonded groups must be contiguously placed. The channel order needs to be maintained when doing the pin assignments to the dedicated RX serial inputs and TX serial outputs (for example: PIN_BC7 and PIN_BC8 for GXBR4D_TX_CH0p and GXBR4D_TX_CH0n TX serial outputs). Channels need to be placed in an ascending order from bottom to top. Swapping of channels, when doing pin assignments, leads to errors.