KSZ9567R datasheet(22/233 Pages) MICROCHIP

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KSZ9567R

DS00002329E-page 22

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The auto-negotiation link-up process is shown in Figure 4-1.

For 1000BASE-T mode, auto-negotiation is always required 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. Afterwards, auto-negotiation can be enabled

or disabled via bit 12 of the PHY Basic Control Register. If auto-negotiation is disabled, the speed is set by bits 6 and

13 of the PHY Basic Control Register, and the duplex is set by bit 8.

If the speed is changed on the fly, the link goes down and either auto-negotiation or parallel detection initiate until a

common speed between the KSZ9567R and its link partner is re-established for a link.

If 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 bit 9 of the PHY Basic Control Regis-

ter, or a link-down to link-up transition occurs (i.e. disconnecting and reconnecting the cable).

After auto-negotiation is completed, the link status is updated in the PHY Basic Status Register, and the link partner

capabilities are updated in the PHY Auto-Negotiation Link Partner Ability Register, PHY Auto-Negotiation Expansion

Status Register, and PHY 1000BASE-T Status Register.

4.1.8

FAST LINK-UP

Link up time is normally determined by the time it takes to complete auto-negotiation. Additional time may be added by

the auto MDI/MDI-X feature. The total link up time from power-up or cable connect is typically a second or more.

FIGURE 4-1:

AUTO-NEGOTIATION AND PARALLEL OPERATION

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