12
ICS1890
100Base-T Physical Media Access [PMA]
Clock Recovery
The Clock Recovery block locks onto the incoming data stream,
extracts the embedded clock, and presents the data synchronized
to the recovered clock. This process produces signals with
very low timing uncertainty and noise (jitter).
In the event that the PLL is unable to lock on to the receive
signal, it generates a not locked signal. The transmit clock
synthesizer provides a center frequency reference for operation
of the clock recovery circuit in the absence of data. The
receive signal detected and not locked signals are both
used by the logic which monitors the receive channel for
errors.
Transmit Clock Synthesizer
The
ICS1890
synthesizes the transmit clock using a PLL to
produce 2.5 MHz for 10Base-T and 25 MHz for 100Base-TX.
Internal clock frequencies of 20 MHz and 125 MHz are also
generated. This allows the use of a low cost 25 MHz crystal
oscillator for a low jitter reference frequency.
Signal Detector
The
ICS1890
Signal Detector is part of the clock recovery
PLL. It detects a Receive Signal Error if no receive signal is
received and detects a PLL Lock Error if the PLL is unable to
lock on to the receive channel signal. A receive channel error
is defined as the loss of receive signal or the loss of PLL lock.
Remote Fault Signaling
Remote fault signaling allows a
link partner to signal receive channel errors on its transmit
channel. It is then possible to establish the integrity of both
the transmit and receive channels. If auto-negotiation is enabled,
the
ICS1890
monitors the receive channel for Fast Link
Pulses or Normal Link Pulses. If an error is detected, the
remote error condition is signaled.
The
ICS1890
is able to report a remote fault detected by its
link partner. When the link partner is an
ICS1890
, a remote
fault will be signaled when it detects a receive signal error. The
definition of a remote fault for a non-
ICS1890
link partner is
undefined, but generally will mean that there is a problem with
the integrity of the link partners receive channel.
Summary of Contents for PHYceiver ICS1890
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