KSZ9031RNX Просмотр технического описания (PDF) - Microchip Technology

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KSZ9031RNX

Gigabit Ethernet Transceiver with RGMII Support

Microchip Technology 

KSZ9031RNX

3.7 Auto-Negotiation

The KSZ9031RNX conforms to the auto-negotiation protocol, defined in Clause 28 of the IEEE 802.3 Specification.

Auto-negotiation allows UTP (unshielded twisted pair) link partners to select the highest common mode of operation.

During auto-negotiation, link partners advertise capabilities across the UTP link to each other, and then compare their

own capabilities with those they received from their link partners. The highest speed and duplex setting that is common

to the two link partners is selected as the operating mode.

The following list shows the speed and duplex operation mode from highest-to-lowest:

• Priority 1: 1000BASE-T, full-duplex

• Priority 2: 1000BASE-T, half-duplex

• Priority 3: 100BASE-TX, full-duplex

• Priority 4: 100BASE-TX, half-duplex

• Priority 5: 10BASE-T, full-duplex

• Priority 6: 10BASE-T, half-duplex

If auto-negotiation is not supported or the KSZ9031RNX link partner is forced to bypass auto-negotiation for 10BASE-

T and 100BASE-TX modes, the KSZ9031RNX sets its operating mode by observing the input signal at its receiver. This

is known as parallel detection, and allows the KSZ9031RNX to establish a link by listening for a fixed signal protocol in

the absence of the auto-negotiation advertisement protocol.

The auto-negotiation link-up process is shown in Figure 3-3.

FIGURE 3-3:

AUTO-NEGOTIATION FLOW CHART

START AUTO-NEGOTIATION

FORCE LINK SETTING

NO

YES

PARALLEL

OPERATION

BYPASS AUTO-NEGOTIATION

AND SET LINK MODE

ATTEMPT AUTO-

NEGOTIATION

LISTEN FOR 100BASE-TX

IDLES

LISTEN FOR 10BASE-T

LINK PULSES

NO

JOIN FLOW

LINK MODE SET?

YES

LINK MODE SET

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 auto-negotiation and parallel detection initiate until a common

speed between KSZ9031RNX 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).

 2016 Microchip Technology Inc.

DS00002117C-page 17

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