XRT83SH314 Просмотр технического описания (PDF) - Exar Corporation

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XRT83SH314

14-CHANNEL T1/E1/J1 SHORT-HAUL LINE INTERFACE UNIT

Exar Corporation 

XRT83SH314

14-CHANNEL T1/E1/J1 SHORT-HAUL LINE INTERFACE UNIT

REV. 1.0.4

1.0 CLOCK SYNTHESIZER

In system design, fewer clocks on the network card could reduce noise and interference. Common clock

references such as 8kHz are readily available to network designers. Network cards that support both T1 and

E1 modes must be able to produce 1.544MHz and 2.048MHz transmission data. The XRT83SH314 has a built

in clock synthesizer that requires only one input clock reference by programming CLKSEL[3:0] in the

appropriate global register. A list of the input clock options is shown in Table 1.

TABLE 1: INPUT CLOCK SOURCE SELECT

CLKSEL[3:0]

0h (0000)

1h (0001)

2h (0010)

3h (0011)

4h (0100)

5h (0101)

6h (0110)

7h (0111)

8h (1000)

9h (1001)

Ah (1010)

Bh (1011)

Ch (1100)

Dh (1101)

Eh (1110)

Fh (1111)

INPUT CLOCK REFERENCE

2.048 MHz

1.544MHz

8 kHz

16 kHz

56 kHz

64 kHz

128 kHz

256 kHz

4.096 MHz

3.088 MHz

8.192 MHz

6.176 MHz

16.384 MHz

12.352 MHz

2.048 MHz

1.544 MHz

The single input clock reference is used to generate multiple timing references. The first objective of the clock

synthesizer is to generate 1.544MHz and 2.048MHz for each of the 14 channels. This allows each channel to

operate in either T1 or E1 mode independent from the other channels. The state of the equalizer control bits in

the appropriate channel registers determine whether the LIU operates in T1 or E1 mode. The second objective

is to generate additional output clock references for system use. The available output clock references are

shown in Figure 2.

14

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