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42 Sun GigaSwift Ethernet Adapter Installation and User’s Guide • February 2003
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.
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-ipg0 set (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.
TABLE 4-4 Forced Mode Parameter
Parameter Description
master-cfg-enable Determines whether or not during the auto-negotiation process
the link clock mastership is setup automatically.
master-cfg-value If the master-cfg-enable parameter is set then the mastership
is not setup automatically but is dependant on the value of
master-cfg-value.Ifthemaster-cfg-value is 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-enable is ignored and the value of
master-cfg-value is key to the link clock mastership. If the
master-cfg-value is 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.