AutoNegotiation
5-5
If both the link partner and the local device are manually given the same
Master/Slave assignment, an error condition exists as indicated by bit 15
of the
1000BASE-T Status Register (1KSTSR) Address 0x0A (10)
. If one
of the link partners is manually assigned a Master/Slave status while the
other is not, the manual assignment takes higher priority during the
resolution process.
When Manual Slave or Manual Master mode is enabled, AutoNegotiation
should also be enabled according to the 802.3u IEEE specification. The
L80600, however, links up to another L80600 when AutoNegotiation is
disabled and one L80600 is manually configured as a Master while the
other is manually configured as a Slave.
An alternative way of specifying Master or Slave mode is to use the
Port_Type strapping option (pin 208) or by writing to the
1000BASE-T
Control Register (1KTCR) Address 0x09
bit 10. When pin 208 is pulled
HIGH or a 1 is written to bit 10, the part advertises that it wants to be a
Master. When pin 208 is pulled LOW or a 0 is written to bit 10, the part
advertises that it wants to be a Slave. If two devices advertise that they
want to both be Master or to both be Slaves, the AutoNegotiation state
machine goes through a random number arbitration sequence to pick
which one is the Master and which is the Slave. Using this method
eliminates the chance of an unresolved link.
5.3 AutoNegotiation
All 1000BASE-T PHYs are required to support AutoNegotiation. The
AutoNegotiation function in 1000BASE-T has four primary purposes:
AutoNegotiation Priority Resolution
AutoNegotiation Master/Slave Resolution
AutoNegotiation Pause/Asymmetrical Pause Resolution
Automatic MDIX Resolution
5.3.1 AutoNegotiation Priority Resolution
To achieve priority resolution, the AutoNegotiation function first provides
a mechanism for exchanging configuration information between two ends
of a link segment and automatically selecting the highest performance
mode of operation supported by both devices.