XRT75VL00D datasheet(86/92 Pages) EXAR

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XRT75VL00D

E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER

REV. 1.0.3

HOW MAJOR PATTERN A IS SYNTHESIZED

MAJOR PATTERN A is created (by the Mapper IC) by:

• Repeating MINOR PATTERN P1 (e.g., 7 clock pulses, followed by a gap) 63 times.

• Upon completion of the 63rd transmission of MINOR PATTERN P1, MINOR PATTERN P2 is transmitted

repeatedly 36 times.

Figure 60 presents an illustration which depicts the procedure that is used to synthesize MAJOR PATTERN A

Hence, MAJOR PATTERN A consists of "(63 x 7) + (36 x 5)" = 621 clock pulses. These 621 clock pulses were

delivered over a period of "(63 x 8) + (36 x 6)" = 720 STS-1 (or 51.84MHz) clock periods.

MAJOR PATTERN B

MAJOR PATTERN B consists of three sub or minor-patterns (which we will refer to as "MINOR PATTERNS P1,

P2 and P3).

MINOR PATTERN P1, which is used to partially synthesize MAJOR PATTERN B, is exactly the same "MINOR

PATTERN P1" as was presented above in Figure 30. Similarly, the MINOR PATTERN P2, which is also used

to partially synthesize MAJOR PATTERN B, is exactly the same "MINOR PATTERN P2" as was presented in

Figure 31.

MINOR PATTERN P3 (which has yet to be defined) consists of a string of six (6) clock pulses, which contains

no gaps. An illustration of MINOR PATTERN P3 is presented below in Figure 61.

FIGURE 59. ILLUSTRATION OF MINOR PATTERN P2

FIGURE 60. ILLUSTRATION OF PROCEDURE WHICH IS USED TO SYNTHESIZE MAJOR PATTERN A

Missing Clock Pulse

MINOR PATTERN P1

MINOR PATTERN P2

Repeats 63 Times

Repeats 36 Times

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