
DS26522 Dual T1/E1/J1 Transceiver 
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1. 
The DS26522 is a 2-channel device that can be software configured for T1, E1, or J1 operation. The DS26522 is a 
MCM composed of two DS26521 die. Each channel is composed of a line interface unit (LIU), framer, HDLC 
controller, and a TDM backplane interface, and is controlled by either an 8-bit parallel port or a serial peripheral 
interface (SPI). Internal impedance matching is provided for both transmit and receive paths reducing external 
component count. The DS26522 is a member of the TEX-series transceiver family and is software compatible with 
the DS26521 single, DS26524 quad, and DS26528 octal transceivers. 
DETAILED DESCRIPTION 
The LIU is composed of a transmit interface, receive interface, and a jitter attenuator. The transmit interface is 
responsible for generating the necessary waveshapes for driving the network and providing the correct source 
impedance depending on the type of media used. T1 waveform generation includes DSX-1 line build-outs as well 
as CSU line build-outs of 0dB, -7.5dB, -15dB, and -22.5dB. E1 waveform generation includes G.703 waveshapes 
for both 75
Ω
 coax and 120
Ω
 twisted cables. The receive interface provides network termination and recovers clock 
and data from the network. The receive sensitivity adjusts automatically to the incoming signal level and can be 
programmed for 0dB to -43dB or 0dB to -12dB for E1 applications and 0dB to -15dB or 0dB to -36dB for T1 
applications. The jitter attenuator removes phase jitter from the transmitted or received signal. The crystal-less jitter 
attenuator requires only a T1 or E1 clock rate, or multiple thereof, for both E1 and T1 applications, and can be 
placed in either transmit or receive data paths. 
On the transmit side, clock, data, and frame-sync signals are provided to the framer by the backplane interface 
section. The framer inserts the appropriate synchronization framing patterns, alarm information, calculates and 
inserts the CRC codes, and provides the B8ZS/HDB3 (zero code suppression) and AMI line coding. The receive-
side framer decodes AMI, B8ZS, and HDB3 line coding, synchronizes to the data stream, reports alarm 
information, counts framing/coding/CRC errors, and provides clock, data, and frame-sync signals to the backplane 
interface section. 
Both transmit and receive paths have access to an HDLC controller. The HDLC controller transmits and receives 
data via the framer block. The HDLC controller can be assigned to any time slot, a portion of a time slot, or to FDL 
(T1) or Sa bits (E1). Each controller has 64-byte FIFOs, reducing the amount of processor overhead required to 
manage the flow of data.  
The backplane interface provides a versatile method of sending and receiving data from the host system. Elastic 
stores provide a method for interfacing to a system backplane, converting from a T1/E1 network to a 2.048MHz, 
4.096MHz, 8.192MHz, 16.384MHz, or N x 64kHz system backplane. The elastic stores also manage slip conditions 
(asynchronous interface). The interleave bus option (IBO) is provided to allow up to eight transceivers to share a 
high-speed backplane. The DS26522 also contains an internal clock adapter useful for the creation of a 
synchronous, high-frequency backplane timing source. 
The parallel port provides access for configuration and status of all the DS26522’s features. Diagnostic capabilities 
include loopbacks, PRBS pattern generation/detection, and 16-bit loop-up and loop-down code generation and 
detection. 
1.1 
Major Operating Modes 
The DS26522 has two major modes of operation: T1 mode and E1 mode. The mode of operation for the LIU is 
configured in the LIU Transmit Receive Control register (
LTRCR
). The mode of operation for the framer is 
configured in the Transmit Master Mode register (
TMMR
) and Receive Master Mode register (
RMMR
). J1 operation 
is a special case of T1 operating mode.