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Subject to Change
VSC7111 Datasheet
Functional Descriptions
This signal is also forwarded to any output that is connected to the corresponding input,
and can be used to squelch a transmitted signal when the connected input goes into an
LOS state. This is how OOB signaling is propagated.
LOS is available when the CLOSON bit, Input LOS register bit 7, is set to 1. LOS is not
available when the bit is set to 0, which disables the LOS circuitry to reduce power
consumption when the LOS function is not required.
2.11
Output Pre-Emphasis
The output pre-emphasis (PE) function of the VSC7111 helps to combat the intersymbol
interference (ISI) of high-speed data as it passes through lossy media. This is
accomplished by shaping the output waveform to boost the magnitude of those
frequency components of the transmitted signal that are most susceptible to
attenuation as it propagates through the transmission media.
The VSC7111 provides flexibility in correcting for transmission losses with two
independent pre-emphasis stages that are additive. Each stage has a different
adjustable time constant associated with it.
Figure 5.
Output Pre-Emphasis Architecture
Output
Level
PE 1
Level
PE 2
Level
The output pre-emphasis consists of two parallel stages, PE 1 and PE 2, that each have
adjustable pre-emphasis level and pre-emphasis decay. The difference between PE 1
and PE 2 is that the range of decay times for PE 2 is longer than for PE 1.
The bits that control the pre-emphasis settings are in the Output PE1 and Output PE2
registers (addresses 20'h and 21'h). For more information about these settings and
registers, see “Output PE 1,” page 31 and “Output PE 2,” page 32.
The following illustrations show the effects of the decay time constants for PE1 and PE2.
Revision 2.0
September 2010
Confidential
Page 20
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
