The reset_pb signal is used to restore the Aurora 64B/66B core to a
known starting state. Upon reset, the core stops the current operation and
re-initializes the channel. It is expected that user_clock is stable
when the reset_pb signal is applied. When the reset_pb
signal is asserted to the Aurora 64B/66B channel partner1, channel partner2 also loses
lock. Channel partner2 regains lock when channel partner1 is out of reset and begins
transmitting valid patterns. On full-duplex cores, the reset_pb signal
resets both the TX and RX sides of the channel. simplex Aurora 64B/66B cores have
similar reset_pb ports for both partners and require a different reset
sequence. Asserting pma_init resets the entire serial transceiver which
eventually resets the Aurora 64B/66B core as well. Also, it is assumed
nit_clk is always stable and the ref_clk is stable
at the time of deassertion of the pma_init signal.