XRT59L921IB Exar Corporation, XRT59L921IB Datasheet - Page 17

• Manufacturer Part Number: XRT59L921IB
• Description: 21 CHANNEL E1 LIU
• Manufacturer: Exar Corporation

Specifications of XRT59L921IB

• Lead Free Status / RoHS Status: Contains lead / RoHS Compliant

REV. 1.2.1
SYSTEM DESCRIPTION
The XRT59L921 is a Twenty-One (21) channel E1 transceiver that provides an electrical interface for
2.048Mbps applications. Each of the twenty-one channels includes a receive circuit that converts an ITU-T
G.703 compliant bipolar signal into a TTL compatible logic levels. Each receiver also includes an LOS (Loss of
Signal) detection circuit. Similarly, in the Transmit Direction, each Transmitter converts TTL compatible logic
levels into a G.703 compatible bipolar signal. The Transmitter may be operated in either a Clock or Clockless
Mode.
Each channel within the XRT59L921 LIU consists of both a Transmit Section and a Receive Section, each of
these sections will be discussed in detail below.
In general, the purpose of the Transmit Section (within each channel of the XRT59L921) is to accept TTL/
CMOS level digital data (from the Terminal Equipment), and to encode it into a format such that it can:
The circuitry that the Transmit Section (within the XRT59L921) uses to accomplish this goal is discussed
below. The Transmit Section of the XRT59L921 consists of the following blocks:
•
•
The Transmit Input Interface accepts either Clock or clockless data from the Terminal Equipment. The manner
in how the Terminal Equipment should apply data to a given channel within the XRT59L921 depends upon
whether the channel is being operated in the Clock or clockless mode.
The user can configure a given channel (within the XRT59L921) to operate in the Clock mode by simply
applying a 2.048MHz clock signal to the TxClk_n input pin (where x denotes a given channel within the
XRT59L921). The XRT59L921 contains circuitry that senses activity on the TxClk_n line. If this circuit senses
activity on the TxClk_n line, then the corresponding channel will automatically be operating in the Clock Mode.
In the Clock Mode, the Terminal Equipment is expected to apply a 2.048MHz clock signal at the TxClk_n input
pin and NRZ data at the TxPOS_n and TxNEG_n input pins. The Transmit Input Interface circuit will sample
the data, at the TxPOS_n and TxNEG_n input pins, upon the falling edge of TxClk_n, as illustrated in
1.0 THE TRANSMIT SECTION
1.
2.
3.
1.1
1.2
Transmit Input Interface
Pulse Shaping Block
Be efficiently transmitted over coaxial- or twistedpair cable at the E1 data rate and
Be reliably received by the Remote Terminal Equipment at the other end of the E1 data link.
Comply with the ITU-T G.703 pulse template requirements, for E1 applications.
The Transmit Input Interface
Operating the Transmitter in the Clock Mode
TWENTY-ONE CHANNEL E1 LINE INTERFACE UNIT
15
XRT59L921
Figure
4.