XRT86L30
SINGLE T1/E1/J1 FRAMER/LIU COMBO
REV. 1.0.1
4.2
R3 Technology (Relayless / Reconfigurable / Redundancy)
Redundancy is used to introduce reliability and protection into network card design. The redundant card in
many cases is an exact replicate of the primary card, such that when a failure occurs the network processor
can automatically switch to the backup card. EXAR’s R3 technology has re-defined DS-1/E1/J1 physical
interface design for 1:1 and 1+1 redundancy applications. Without relays and one Bill of Materials, EXAR
offers multi-port, integrated Framer/LIU solutions to assist high density aggregate applications and framing
requirements with reliability. The following section can be used as a reference for implementing R3 Technology
with EXAR’s world leading Framer/LIU combo.
4.2.1
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
XRT86L30 Framer/LIU. EXAR offers features that are tailored to redundancy applications while reducing the
number of components and providing system designers with solid reference designs.
4.2.2
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
4.2.3
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 physical interface are described separately.
4.2.4
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 9. for a simplified block diagram of the transmit section for a 1:1 and 1+1 redundancy.
F
IGURE 9. SIMPLIFIED BLOCK DIAGRAM OF THE TRANSMIT INTERFACE FOR 1:1 AND 1+1 REDUNDANCY
Backplane Interface
Primary Card
XRT86L30
1:2
0.68uF
Tx
T1/E1 Line
Internal Impedence
Backup Card
XRT86L30
1:2
0.68uF
Tx
Internal Impedence
145
EXAR [ EXAR CORPORATION ]
