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Software Developer’s Manual 171
Ethernet Interface
Table 8-9. GMII/MII Mode – Force Link
CTRL.FRCSPD = CTRL.FRCDPLX = CTRL.SLU = 1b
8.6.5 Loss of Signal/Link Status Indication
For the 82546GB/EB and 82545GM/EM, the internal LOS signal allows for indication of physical
link status to the Ethernet controller’s MAC.
For the
82544GC/EI, the LOS input is provided to allow for indication of physical link status to
the Ethernet controller. When the
82544GC/EI is configured in TBI mode, the input is typically
connected to the loss-of-signal connection from the optics while in internal PHY mode.
If the LSC (Link Status Change) interrupt is enabled, the hardware posts an interrupt to be serviced
by the software driver when the link goes up or down. See Section 3.4.3 for more details.
8.6.5.1 Internal Serdes Mode
1
When asserted, LOS indicates there is no activity on the fiber due to either an unplugged cable or a
defective optical device. An assertion on LOS implies the link is not available and the hardware is
disabled. This is true whether the link is forced by the Set Link Up bit (CTRL.SLU) or if the
Ethernet controller is configured to perform Auto-Negotiation. When Auto-Negotiation is enabled,
the Ethernet controller is forced to restart Auto-Negotiation but does not complete the negotiation
process until the LOS is deasserted.
8.6.5.2 Internal PHY Mode
While in internal PHY mode, an internal signal provides status of the physical link as indicated by
the PHY. Indication that the link is not up disables MAC operation. Upon determination of a valid
link, the assertion of the internal link signal asserts the LSC interrupt (if enabled) to indicate to the
software driver to check the link status.
Control Bit Effect on Control Bits
CTRL.FD Set by software.
CTRL.SLU Set by software, and assumed PHY is also forced to assert link.
CTRL.RFCE Set by software for the desired mode of operation.
CTRL.TFCE Set by software for the desired mode of operation.
CTRL.SPEED Set by software.
STATUS.FD Reflects the value of CTRL.FD.
STATUS.LU Reflects CTRL.SLU set and internal link status.
STATUS.SPEED Reflects CTRL.SPEED.
1. TBI mode for the 82544GC/EI.