Draft 6/5/00
Full/Half Duplex Mode
2-43
Copyright 2000 by LSI Logic Corporation. All rights reserved.
The TP receiver senses missing data transitions in order to detect the
receive SOI pulse. Once the SOI pulse is detected, data reception is
ended and the CRS and RX_DV pins are deasserted.
2.5 Full/Half Duplex Mode
Half-Duplex mode is the CSMA/CD operation defined in IEEE 802.3. It
allows transmission or reception, but not both at the same time. Full-
Duplex operation is a mode that allows simultaneous transmission and
reception. Full duplex in the 10 Mbits/s mode is identical to operation in
the 100 Mbits/s mode.
The device can be forced into either the Full- or Half-Duplex mode, or
the device can use AutoNegotiation to autoselect Full/Half-Duplex
operation. When the device is placed in Full-Duplex mode:
The collision function is disabled, and
TX_EN to CRS loopback is disabled
2.5.1 Forcing Full/Half Duplex Operation
To independently force a channel into either the Full- or Half-Duplex
mode, set the Duplex Mode Select (DPLX) bit in the MI serial port
Control register, or assert the DPLX pin, assuming that AutoNegotiation
is not enabled with the ANEG_EN bit in the MI serial port Control
register.
The device automatically configures itself for Full- or Half-Duplex mode.
To do this, the device uses the AutoNegotiation algorithm to advertise
and detect Full and Half Duplex capabilities to and from a remote device.
To enable AutoNegotiation, set the AutoNegotiation Enable (ANEG_EN)
bit in the MI serial port Control register or assert the ANEG pin.
To select the advertised Full/Half Duplex capability, appropriately set the
bits in the MI serial port AutoNegotiation Advertisement register.
AutoNegotiation functionality is described in more detail in
Section
2.2.11, “Link Integrity and AutoNegotiation”
.