xrt5997 Exar Corporation, xrt5997 Datasheet - Page 19

• Manufacturer Part Number: xrt5997
• Description: Xrt5997 -seven Channel E1 Line Interface Unit
• Manufacturer: Exar Corporation

SYSTEM DESCRIPTION
The XRT5997 device is a Seven (7) channel E1
transceiver that provides an electrical interface for
2.048Mbps applications. Each of the seven 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 “Clocked”
or “Clockless” Mode.
Each channel within the XRT5997 LIU device consists
of both a Transmit Section and a Receive Section,
each of these sections will be discussed in detail
below.
1.0 The Transmit Section
In general, the purpose of the “Transmit Section”
(within each channel of the XRT5997 device) 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
XRT5997 device) uses to accomplish this goal is
discussed below.
XRT5997 device consists of the following blocks:
1. Be efficiently transmitted over coaxial- or twisted-
2. Be reliably received by the Remote Terminal
3. Comply with the ITU-T G.703 pulse template
Transmit Input Interface
Pulse Shaping Block
pair cable at the E1 data rate; and
Equipment at the other end of the E1 data link.
requirements, for E1 applications.
Rev. 1.0.0
The Transmit Section of the
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1.1
The Transmit Input Interface accepts either “clocked”
or “clockless” data from the Terminal Equipment. The
manner in how the Terminal Equipment should apply
data to a given channel within the XRT5997 device
depends upon whether the channel is being operated in
the “clocked” or “clockless” mode.
1.2.1 Operating the Transmitter in the Clocked
The user can configure a given channel (within the
XRT5997 device) to operate in the “Clocked” mode by
simply applying a 2.048MHz clock signal to the
“TxClk_x” input pin (where x denotes a given channel
within the XR5997 device). The XRT5997 device
contains some circuitry that sense activity on the
“TxClk_x” line. If this circuit senses activity on the
“TxClk_x” line, then the corresponding channel will
automatically be operating in the “Clocked” Mode.
In the Clocked Mode, the Terminal Equipment is
expected to apply a 2.048MHz clock signal at the
TxClk_x input pin and NRZ data at the TxPOS_x and
TxNEG_x input pins. The “Transmit Input Interface”
circuit will sample the data, at the TxPOS_x and
TxNEG_x input pins, upon the falling edge of TxClk_x,
as illustrated in Figure 3.
Mode
The Transmit Input Interface
XRT5997