Rainbow Electronics DS21458 - Manual (Page 158)

DS21455/DS21458 Quad T1/E1/J1 Transceivers
158 of 270
25. LINE INTERFACE UNIT (LIU)
The LIU in the DS21455/DS21458 contains three sections: the receiver, which handles clock and data
recovery; the transmitter, which wave-shapes and drives the network line; and the jitter attenuator. These
three sections are controlled by the line interface control registers (LIC1–LIC4), which are described
below. The LIU has its own T1/E1 mode select bit and can operate independently of the framer function.
The DS21455/DS21458 can switch between T1 or E1 networks without changing any external
components on either the transmit or receive side.
Figure 25-1 and Figure 25-2 show basic balanced and
unbalanced network connections using minimal components. In this configuration the device can connect
to T1, J1, or E1 (75Ω or 120Ω) without any component change. The receiver can adjust the 120Ω
termination to 100Ω or 75Ω. The transmitter can adjust its output impedance to provide high return loss
characteristics for 120Ω, 100Ω, and 75Ω lines. Other components may be added to this configuration in
order to meet safety and network protection requirements. This is covered in Section
25.8 (Recommended
Circuits).
Figure 25-1. Basic Balanced Network Connections
TTIP
TRING
RTIP
RRING
DS21455/
DS21458
Tx
Rx
0.047 mF
60 W* 60 W*
0.01 mF
*USE 60 W WHEN USING INTERNAL TERMINATION FEATURE.