FBFM2112F897CSLJLS View Datasheet(PDF) - Intel

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FBFM2112F897CSLJLS

Intel® FM2112 24-Port 10G/1G Ethernet Switch Chip

Intel 

Intel® FM2112 24-Port 10G/1G Ethernet Switch Chip Data Sheet

3.1.2.4

Transmitter Equalization (Pre-emphasis)

Each transmitter has a first-order equalization function implemented as

a pre-emphasis current (sometimes termed, “de-emphasis” because

the lower frequency components of the signal are reduced, or de-

emphasized). Equalization helps reduce the amount of inter-symbol

interference by counteracting the effects of frequency dependent

transmission loss. The effects of pre-emphasis are shown in The

FM2112 SerDes uses a fixed, optimized amount of Rx equalization to

complement the pre-emphasis function.

By setting the DEQ bits in the SERDES_CNTL_1 Register (see

Table 130), the ratio of equalization current to driver current varies

from 0.0 (equalization off) to a maximum of 0.65. With a setting of

0.65, for example, driver current is reduced from the nominal value

(set with High Drive, Low Drive and DTX bits) by 65% for those bits

where equalization is in effect. Equalization is in effect when successive

1's or 0's are sent. The first bit after a transition is not affected, but the

second and all subsequent consecutive bits are affected by the drive

current reduction until another transition occurs.

The overall effect of this pre-emphasis function is that of a high-pass

filter, which can be used to compensate for the low-pass characteristic

of transmission media. The FM2112 SerDes uses a fixed, optimized

amount of Rx equalization to complement the pre-emphasis function.

Figure 6.

Driver Equalization

21

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