188.8.131.52.1. High Speed Transmitter Line Buffer
The transmitter differential I/O buffer converts the serialized bit stream to an electrical signal suitable for transmission across a cable or PCB channel. The Attenuation Value (VOD) parameter controls the transmitter swing strength, and pre-cursor and post-cursor taps of the feed-forward equalization (FFE) circuit help shape the transmitter output waveform.
On FPGA device configuration and initial reset, the transceiver supply voltage is driven on the TX lines. During this state, both the transmitter and TX buffer are disabled. The TX buffer is in tristate during the start-up sequence. When both the transmitter and TX buffer are enabled, the TX buffer drives normal differential data, and the differential impedance on both TX and RX lines is in the range of 80 (minimum), 100 (typical), 120 (maximum) Ω. For more details on the termination modes, refer to the description for PMA attribute code 0x002B in the PMA Attribute Codes section.
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