LAN8808D datasheet(34/80 Pages) MICROCHIP

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LAN8808D

DS00005833C-page 34

• Master-Slave configuration set to Slave via the Auto Negotiation Master Slave Control Register

Wait 10 ms prior to testing the pairs.

In this scenario, for each of the four twisted pairs, LinkMD should only return Open or Short along with a distance.

• Open with “distance” providing the correct cable length indicates a good cable

• Short or Open with any other distance indicates a bad cable

After running the cable diagnostics, perform another software reset via the Basic Control Register

5.7.2

LINKMD WITH FULLY PASSIVE LINK PARTNER

In this scenario, the remote end of the cable is connected to a Link Partner. The Link Partner must be powered down or

configured to be in the following passive state:

• Auto Negotiation disabled

• Auto MDI/MDI-X disabled

Prior to running the cable diagnostics, perform a software reset via the Basic Control Register. After reset, the following

must be configured:

• Auto Negotiation disabled via the Digital Debug Control 1 Register

• Auto MDI/MDI-X disabled via the Digital Debug Control 1 Register

• Full Duplex set via the Basic Control Register

• Link Speed set to 1000 Mbps via the Basic Control Register

• Master-Slave configuration set to Slave via the Auto Negotiation Master Slave Control Register

Wait 10 ms prior to testing the pairs.

In this scenario, for each of the four twisted pairs, LinkMD will return Open or Short along with a distance, or Normal.

• Normal indicates a good cable which is properly terminated at the Link Partner. Due to no TDR reflections, no

cable distance is available with this result (VCT[7:0] is invalid).

• Open or Short indicates a bad cable or improper Link Partner termination. VCT[7:0] indicates the distance to the

cable fault.

After running the cable diagnostics, perform another software reset via the Basic Control Register.

5.7.3

LINKMD WITH PARTIALLY ACTIVE LINK PARTNER

In this scenario, the remote end of the cable is connected to a Link Partner. The Link Partner is powered up and in the

following state:

• Auto Negotiation may be enabled, disabled or unknown

• Auto MDI/MDI-X is disabled, but we are able to selectively configure MDI or MDI-X, as required for the LinkMD

tests

Prior to running the cable diagnostics, perform a software reset via the Basic Control Register. After reset, the following

must be configured:

• Auto Negotiation disabled via the Digital Debug Control 1 Register

• Auto MDI/MDI-X disabled via the Digital Debug Control 1 Register

• Full Duplex set via the Basic Control Register

• Link Speed set to 1000 Mbps via the Basic Control Register

• Master-Slave configuration set to Slave via the Auto Negotiation Master Slave Control Register

Wait 10 ms prior to testing the pairs.

The LinkMD test is first run with the Link Partner in MDI mode on twisted pairs B, C, and D.

The LinkMD test is then run with the Link Partner in MDI-X mode on twisted pair A.

• Normal indicates a good cable which is properly terminated at the Link Partner. Due to no TDR reflections, no

cable distance is available with this result (VCT[7:0] is invalid).

• Open or Short indicates a bad cable or improper Link Partner termination. VCT[7:0] indicates the distance to the

cable fault.

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