11

FN7450.1

May 17, 2005

Decoding is based on the EL4543 encoding scheme, as

described in Figure 27 and Table 1. The scheme is a three-

level system, which has been designed such that the sum of

the common mode voltages results in a fixed average DC

level with no AC content. This eliminates the effect of EMI

radiation into the common mode signals along the twisted

pairs of the cable

The common mode voltages are initially extracted by the

EL9111 from the three input pairs. These are then passed to

an internal logic decoding block to provide Horizontal and

FIGURE 27. H & V SYNCS ENCODED

TABLE 1. H AND V SYNC DECODING

RED CM

GREEN CM

BLUE CM

Mid

High

Low

Low

Low

High

Low

Mid

Low

High

Low

High

Mid

High

Low

Mid

Low

High

High

High

NOTE: Level ‘Mid’ is halfway between ‘High’ and ‘Low’

TIME (0.5ms/DIV)

BLUE CM

OUT (CH A)

GREEN CM

OUT (CH B)

RED CM

OUT (CH C)

EL9111, EL9112