XRT83SH38 datasheet(39/78 Pages) EXAR

39 / 78 page

XRT83SH38

REV. 1.0.7

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

5.2

Line Card Redundancy

Telecommunication system design requires signal integrity and reliability. When a T1/E1 primary line card has

a failure, it must be swapped with a backup line card while maintaining connectivity to a backplane without

losing data. System designers can achieve this by implementing common redundancy schemes with the

XRT83SH38 LIU. EXAR offers features that are tailored to redundancy applications while reducing the number

of components and providing system designers with solid reference designs.

RLOS and DMO

If an RLOS or DMO condition occurs, the XRT83SH38 reports the alarm to the individual status registers on a

per channel basis. However, for redundancy applications, an RLOS or DMO alarm can be used to initiate an

automatic switch to the back up card. For this application, two global pins RLOS and DMO are used to indicate

that one of the 8-channels has an RLOS or DMO condition.

Typical Redundancy Schemes

• 1:1 One backup card for every primary card (Facility Protection)

• 1+1 One backup card for every primary card (Line Protection)

• ·N+1 One backup card for N primary cards

5.2.1

1:1 and 1+1 Redundancy Without Relays

The 1:1 facility protection and 1+1 line protection have one backup card for every primary card. When using

1:1 or 1+1 redundancy, the backup card has its transmitters tri-stated and its receivers in high impedance. This

eliminates the need for external relays and provides one bill of materials for all interface modes of operation.

For 1+1 line protection, the receiver inputs on the backup card have the ability to monitor the line for bit errors

while in high impedance. The transmit and receive sections of the LIU device are described separately.

5.2.2

Transmit Interface with 1:1 and 1+1 Redundancy

The transmitters on the backup card should be tri-stated. Select the appropriate impedance for the desired

mode of operation, T1/E1/J1. A 0.68uF capacitor is used in series with TTIP for blocking DC bias. See

Figure 27. for a simplified block diagram of the transmit section for a 1:1 and 1+1 redundancy.

FIGURE 27. SIMPLIFIED BLOCK DIAGRAM OF THE TRANSMIT INTERFACE FOR 1:1 AND 1+1 REDUNDANCY

T1/E1 Line

Backplane Interface

Primary Card

Backup Card

XRT83SH38

0.68uF

Internal Impedence

1:2

XRT83SH38

Internal Impedence

XRT83SH38 Datasheet(PDF) 39 Page - Exar Corporation

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