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XRT83SL314

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

Exar Corporation 

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

XRT83SL314

REV. 1.0.1

2.1 Line Termination (RTIP/RRING)

2.1.1 CASE 1: Internal Termination

The input stage of the receive path accepts standard T1/E1/J1 twisted pair or E1 coaxial cable inputs through

RTIP and RRING. The physical interface is optimized by placing the terminating impedance inside the LIU.

This allows one bill of materials for all modes of operation reducing the number of external components

necessary in system design. The receive termination (along with the transmit termination) impedance is

selected by programming TERSEL[1:0] to match the line impedance. Selecting the internal impedance is

shown in Table 2.

TABLE 2: SELECTING THE INTERNAL IMPEDANCE

TERSEL[1:0]

RECEIVE TERMINATION

0h (00)

100Ω

1h (01)

110Ω

2h (10)

75Ω

3h (11)

120Ω

The XRT83SL314 has the ability to switch the internal termination to "High" impedance by programming

RxTSEL in the appropriate channel register. For internal termination, set RxTSEL to "1". By default, RxTSEL

is set to "0" ("High" impedance). For redundancy applications, a dedicated hardware pin (RxTSEL) is also

available to control the receive termination for all channels simultaneously. This hardware pin takes priority

over the register setting if RxTCNTL is set to "1" in the appropriate global register. If RxTCNTL is set to "0", the

state of this pin is ignored. See Figure 4 for a typical connection diagram using the internal termination.

FIGURE 4. TYPICAL CONNECTION DIAGRAM USING INTERNAL TERMINATION

XRT83SL314 LIU

RTIP

Receiver

Input

RRING

Internal Impedance

1:1

Line Interface T1/E1/J1

One Bill of Materials

16

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