The transceiver TX uses a reset state machine to control the reset process. The transceiver TX is partitioned into two reset regions, TX PMA and TX PCS. The partition allows TX initialization and reset to be operated only in sequential mode, as shown in the following figure.
The initializing TX must use GTTXRESET in sequential mode. Activating the GTTXRESET input can automatically trigger a full asynchronous TX reset. The reset state machine executes the reset sequence, as shown in the figure below, covering the whole TX PMA, TX DAPI, TX buffer bypass (if used), and TX PCS. During normal operation, when needed, sequential mode allows you to reset the TX from activating TXPMARESET and continue the reset state machine until TXRESETDONE transitions from Low to High. TXRESETDONE does not assert in single mode.
The TX reset state machine does not reset the PCS until TXUSERRDY is detected High. Drive TXUSERRDY High after all clocks used by the application including TXUSRCLK are shown as stable.