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XRT7250
DS3/E3 FRAMER IC
MARCH 2001
REV. 1.1.1
GENERAL DESCRIPTION
the local terminal equipment to receive data from re-
mote terminal equipment.
The XRT7250 DS3/E3 Framer IC is designed to ac-
cept “User Data” from the Terminal Equipment and in-
sert this data into the “payload” bit-fields within an
“outbound” DS3/E3 Data Stream. Further, the Framer
IC is also designed to receive an “inbound” DS3/E3
Data Stream (from the Remote Terminal Equipment)
and extract out the “User Data”.
The Microprocessor Interface is used to configure the
Framer IC in different operating modes and monitor
the performance of the Framer.
The Performance Monitor Section consists of a large
number of "Reset-upon-Read" and "Read-Only" reg-
isters that contain cumulative and "one-second" sta-
tistics that reflect the performance/health of the Fram-
er IC/system.
The XRT7250 DS3/E3 Framer is designed to support
full-duplex data flow between Terminal Equipment
and an LIU (Line Interface Unit) IC. The Framer De-
vice will transmit, receive and process data in the
DS3-C-bit Parity, DS3-M13, E3-ITU-T G.751 and E3-
ITU-T G.832 Framing Formats.
FEATURES
• Transmits, Receives and Processes data in the
DS3-C-bit Parity, DS3-M13, E3-ITU-T G.751 and
E3-ITU-T G.832 Framing Formats.
The XRT7250 DS3/E3 Framer IC consists of four sec-
tions.
• Interfaces to all Popular Microprocessors
• Integrated Framer Performance Monitor
• Available in a 100 Pin PQFP package
• Operating Temperature -40°C to +85°C
The Transmit Section, includes a Transmit Payload
Data Input Interface, a Transmit Overhead data Input
Interface Section, a Transmit HDLC Controller, a
Transmit E3/DS3 Framer block and a Transmit LIU In-
terface Block which permits the Terminal Equipment
to transmit data to a remote terminal.
APPLICATIONS
• Interface to DS3 or E3 Networks
• CSU/DSU Equipment.
• PCM Test Equipment
• Fiber Optic Terminals
The Receive Section, consists of a Receive LIU Inter-
face, a Receive E3/DS3 Framer, a Receive HDLC
Controller, a Receive Payload Data Output Interface,
and a Receive Overhead Data Interface which allows
BLOCK DIAGRAM OF XRT7250
TxOHFrame
TxOHEnable
Transmit Overhead
Input
Interface Block
TxOH
TxOHClk
TxOHIns
TxOHInd
TxPOS
TxSer
TxNib[3:0]
TxInClk
Transmit
Payload Data
Input
Transmit LIU
Interface
Block
Transmit DS3/E3
Framer Block
TxNEG
Interface Block
TxNibClk
TxFrame
TxLineClk
MOTO
D[7:0]
A[8:0]
Int
CS
Rd_DS
Tx LAPD Buffer/
Controller
Microprocessor
Interface
Wr_RW
Rdy_Dtck
Rx LAPD Buffer/
Controller
Reset
ALE_AS
RxSer
RxNib[3:0]
RxOutClk
RxNibClk
RxFrame
RxPOS
Receive Payload
Data Output
Interface Block
Receive LIU
Interface
Block
Receive DS3/E3
Framer Block
RxNEG
RxLineClk
RxOHFrame
RxOH
Receive Overhead
Output
Interface Block
RxOHClk
RxOHEnable
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (510) 668-7000 • FAX (510) 668-7017 • www.exar.com