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100BASE-TX DIGITAL BLOCKS
LINK MONITOR
The Link Monitor process is responsible for determining whether the underlying receive channel is providing
reliable data. Failure of the underlying channel typically causes the PMA' s client to suspend normal actions. The
Link Monitor process takes advantage of the PMD sublayer' s continuously-signaled transmission scheme, which
provides the PMA with a continuous indication of signal detection on the channel through SIGNAL_STATUS as
communicated by the PMD_SIGNAL.indicated primitive. It responds to control by Auto-negotiation.
The Link Monitor process monitors SIGNAL_STATUS and sets link_status to FAIL whenever SIGNAL_STATUS is
OFF or when Auto-negotiation sets link_control to DISABLE. The link is deemed to be reliably operating when
SIGNAL_STATUS has been continuously ON for a certain period of time. If so qualified, Link Monitor sets
link_status to READY in order to synchronize with Auto-negotiation. Auto-negotiation permits full operation by
setting link_control to ENABLE. Figure 4-8 shows the state diagram for the Link Monitor
link_control = SCAN_FOR_CARRIER
4-12
Figure 4-8. Link Monitor State Diagram of KS8910
KS8910 100/10 Mbps ETHERNET TRANSCEIVER
BEGIN(pwon_reset)
(SIGNAL_STATUS = OFF) +
(link_control = DISABLE) +
(faulting = TRUE)
LINK DOWN
link_status=FAIL
SIGNAL_STATUS = ON
HYSTERESIS
Start stabilize_timer
stabilize_timer_done
LINK READY
link_status=READY
link_control = ENABLE
LINKUP
link_status=OK
Preliminary Spec. ver
1.4
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