autoneg_enable
When the autoneg_enable input signal is set to 1, auto-negotiation
begins automatically at power-up, or if the carrier signal is lost, or if the input
restart_negotiation signal is cycled from a 0 to a 1. All of
the Ability input signals as well as the two input signals PAUSE
and ASM_DIR are tied Low or High to indicate the capability of the
hardware. The nonce_seed[7:0] input must be set to a unique
non-zero value for every instance of the auto-negotiator. This is important to
guarantee that no dead-locks occur at power-up. If two link partners connected
together attempt to auto-negotiate with their nonce_seed[7:0]
inputs set to the same value, the auto-negotiation fails continuously. The
pseudo_sel input is an arbitrary selection that is used to
select the polynomial of the random bit generator used in bit position 49 of the DME
pages used during auto-negotiation. Any selection on this input is valid and does
not result in adverse behavior.
Link Control
When auto-negotiation begins, the various link control signals are activated, depending on the disposition of the corresponding Ability inputs for those links. Subsequently, the corresponding link status signals are monitored by the ANIPC hardware for an indication of the state of the various links that are connected. If particular links are unused, the corresponding link control outputs are unconnected, and the corresponding link-status inputs should be tied Low. During this time, the ANIPC hardware sets up a communication link with the link partner and uses this link to negotiate the capabilities of the connection.
Auto-Negotiation Complete
When Auto-Negotiation is complete, the autoneg_complete output
signal is asserted. In addition, the output signal an_fec_enable is
asserted if the Forward Error Correction hardware is to be used; the output signal
tx_pause_en is asserted if the transmitter hardware is allowed
to generate PAUSE control packets, the output signal rx_pause_en is
asserted if the receiver hardware is allowed to detect PAUSE control packets, and
the output link control of the selected link is set to its mission mode value
(bin)11.