Sun Microsystems X1150A manual Gigabit Link Clock Mastership Controls, Interpacket Gap Parameters

Gigabit Link Clock Mastership Controls

The concept of link clock mastership introduced with one gigabit twisted-pair technology. This concept requires one side of the link to be the master that provides the link clock and the other to be the slave that uses the link clock. Once this relationship is established the link is up, and data can be communicated. Two Physical layer parameters control whether your side is the master or the slave or whether mastership is negotiated with the link partner. Those parameters are as follows.

TABLE 4-4Forced Mode Parameter

ParameterDescription

master-cfg-enableDetermines whether or not during the auto-negotiation process the link clock mastership is setup automatically.

master-cfg-valueIf the master-cfg-enableparameter is set then the mastership is not setup automatically but is dependant on the value of master-cfg-value. If the master-cfg-valueis set then the physical layer expects the local device to be the link master. If it is not set then it expects the link partner to be the master.

If Auto-negotiation is not enabled then the value of master-cfg-enableis ignored and the value of master-cfg-valueis key to the link clock mastership. If the master-cfg-valueis set then the physical layer expects the local device to be the link master. If it’s not set then it expects the link partner to the master.

Caution –Do not adjust the link clock mastership parameters unless you clearly understand the settings of the link partner. Incorrect link clock mastership configuration results in link up failure.

Interpacket Gap Parameters

The ce device supports a programmable mode called enable-ipg0.

When a driver receives a packet with enable-ipg0set (the default), it adds an additional time delay before transmitting the packet. This delay, set by the ipg0 parameter, is in addition to the delay set by the ipg1 and ipg2 parameters. The additional ipg0 delay helps to reduce collisions.

42 Sun GigaSwift Ethernet Adapter Installation and User’s Guide • February 2003