XRT83SL30IV(2003) 查看數據表（PDF） - Exar Corporation

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XRT83SL30IV
(Rev.:2003)

SINGLE-CHANNEL T1/E1/J1 SH TRANSCEIVER WITH CLOCK RECOVERY AND JITTER ATTENUATOR

Exar Corporation 

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XRT83SL30

SINGLE-CHANNEL T1/E1/J1 SH TRANSCEIVER WITH CLOCK RECOVERY AND JITTER ATTENUATOR

PRELIMINARY

REV. P1.0.4

FIGURE 13. SIMPLIFIED DIAGRAM FOR E1 IN EXTERNAL TERMINATION MODE (RXTSEL= 0)

XRT83SL30 LIU

9.1 Ω

1:2

TTIP

TRING

RTIP

9.1 Ω

75 Ω

RRING

1:1

75 Ω

75 Ω

TRANSMITTER

TRANSMIT TERMINATION MODE

In Hardware mode, TXTSEL (Pin 45) can be tied “High” to select internal termination mode or tied “Low” for

external termination. In Host mode, bit 6 in the appropriate register is set “High” to select the internal

termination mode for the transmit channel, see Table 19, “Microprocessor Register #1 bit description,” on

page 44.

TABLE 8: TRANSMIT TERMINATION CONTROL

TXTSEL

0

1

TX TERMINATION

EXTERNAL

INTERNAL

TX TRANSFORMER RATIO

1:2.45

1:2

For internal termination, the transformer turns ratio is always 1:2. In internal mode, no external resistors are

used. An external capacitor of 0.68µF is used for proper operation of the internal termination circuitry, see

Figure 11.

TABLE 9: TERMINATION SELECT CONTROL

TERSEL1

0

0

1

1

TERSEL0

0

1

0

1

TERMINATION

100Ω

110Ω

75Ω

120Ω

EXTERNAL TRANSMIT TERMINATION MODE

By default the XRT83SL30 is set for external termination mode at power up or at Hardware reset.

When external transmit termination mode is selected, the internal termination circuitry is disabled. The value of

the external resistors is chosen for a specific application according to the turns ratio selected by TRATIO (Pin

26) in Hardware mode or bit 0 in the appropriate register in Host mode, see Table 10 and Table 21,

“Microprocessor Register #3 bit description,” on page 49. Figure 12 is a simplified block diagram for T1 (100Ω)

in the external termination mode. Figure 13 is a simplified block diagram for E1 (75Ω) in the external

termination mode.

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