KSZ9031MNX Datasheet, PDF (22/76 Pages) Micrel Semiconductor – The KSZ9031MNX is a completely integrated triple-speed (10Base-T/100Base-TX/1000Base-T) Ethernet physicallayer transceiver for transmission and reception of data on standard CAT-5 unshielded twisted pair (UTP) cable.

Micrel, Inc.
KSZ9031MNX
Figure 3. Auto-Negotiation Flow Chart
For 1000Base-T mode, auto-negotiation is required and always used to establish a link. During 1000Base-T auto-
negotiation, the master and slave configuration is first resolved between link partners. Then the link is established with the
highest common capabilities between link partners.
Auto-negotiation is enabled by default after power-up or hardware reset. After that, auto-negotiation can be enabled or
disabled through register 0h, bit [12]. If auto-negotiation is disabled, the speed is set by register 0h, bits [6, 13] and the
duplex is set by register 0h, bit [8].
If the speed is changed on the fly, the link goes down and either auto-negotiation or parallel detection initiates until a
common speed between KSZ9031MNX and its link partner is re-established for a link.
If the link is already established and there is no change of speed on the fly, the changes (for example, duplex and pause
capabilities) will not take effect unless either auto-negotiation is restarted through register 0h, bit [9], or a link-down to link-
up transition occurs (that is, disconnecting and reconnecting the cable).
After auto-negotiation is completed, the link status is updated in register 1h, bit [2], and the link partner capabilities are
updated in registers 5h, 6h, and Ah.
The auto-negotiation finite state machines use interval timers to manage the auto-negotiation process. The duration of
these timers under normal operating conditions is summarized in Table 2.
October 2012
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M9999-103112-1.0