XRT7250 datasheet(110/463 Pages) EXAR

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DS3/E3 FRAMER IC

XRT7250

REV. 1.1.1

ceive E3 Framer conditions or upon the content of the

Tx MA Byte register (Address = 0x2A).

FERF and FEBE values are based upon Receive E3

Framer Conditions

If the user selects Receive E3 Framer conditions,

then the Transmit E3 Framer will set and clear the

FERF and FEBE bit-fields in response to the following

conditions.

a. FERF Bit-field

If the Receive E3 Framer (on the same UNI chip) is

currently experiencing an LOS, AIS, or LOF condi-

tion, then the Transmit E3 Framer will set the FERF

bit-field (in the outbound E3 frame) to "1". Converse-

ly, if the Receive E3 Framer is not experiencing any of

these conditions, then the Transmit E3 Framer will set

the FERF bit-field (in the outbound E3 frame) to "0".

b. FEBE bit-field

If the Receive E3 Framer detects a BIP-8 error in the

incoming E3 frame, then the Transmit E3 Framer will

set the FEBE bit-field (in the outbound E3 frame) to

"1". Conversely, if the Receive E3 Framer does not

detect a BIP-8 error in the incoming E3 frame, then

the Transmit E3 Framer will set the FEBE bit-field (in

the E3 outbound E3 frame) to "0".

FEBE and FERF values are based upon the contents

of the Tx MA Byte register

If the user selects the contents of the Tx MA Byte reg-

ister, then whatever value has been written into bit 7

(FERF), within the Tx MA Byte register (Address =

2Ah), will be the value of the FERF bit-field, in the

outbound E3 frame. Likewise, whatever value has

been written into Bit 6 (FEBE) within the Tx MA Byte

outbound E3 frame.

Writing a "1" into Bit 0 (MAx) within the Tx E3 Config-

uration register configures the Transmit E3 Framer to

set the FERF and FEBE bit-fields (in the outbound E3

frames) to values based upon Receive E3 Framer

conditions. Writing a "0" into this bit-field configures

the Transmit E3 Framer to set the FEBE and FEBE

bit-fields (in the outbound E3 frames) to the values

written into bit-fields 6 and 7 within the Tx MA Byte

2.3.6.2

Transmit E3 LAPD Configuration Reg-

ister (E3, ITU-T G.832)

Bit 3 - Auto Retransmit

This Read/Write bit-field allows the user to configure

the LAPD Transmitter to either transmit the LAPD

Message frame only once, or repeatedly at one-sec-

ond intervals.

Writing a "0" to this bit-field configures the LAPD

Transmitter to transmit the LAPD Message frame

once. Afterwards, the LAPD Transmitter will halt

transmission, until it has commanded to transmit an-

other LAPD Message frame.

Writing a "1" to this bit-field configures the LAPD

Transmitter to transmit the LAPD Message frame re-

peatedly at One-Second intervals. In this configura-

tion, the LAPD Transmitter will repeat its transmission

of the LAPD Message frame until it has been dis-

abled.

Bit 1 - TxLAPD Message Length Select

This Read/Write bit-field permits the user to select

the length of the outbound LAPD Message frame.

Setting this bit-field to "0" configures the outbound

LAPD Message frame to be 76 bytes in length. Set-

ting this bit-field to "1" configures the outbound LAPD

Message frame to be 82 bytes in length.

Bit 0 - TxLAPD Enable

This Read/Write bit-field allows the user to enable or

disable the LAPD Transmitter. The LAPD Transmitter

must be enabled before it can be commanded to

transmit a LAPD Message frame (containing a PMDL

message) via the outbound DS3 frames, to the Far-

End Terminal.

Writing a "0" disables the LAPD Transmitter (default

condition). Writing a "1" enables the LAPD Transmit-

ter.

NOTE: For information on the LAPD Transmitter, please see

Section 3.2.3.2.

TXE3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)

BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 0

Not Used

Auto

Retransmit

Not Used

TxLAPD

Msg Length

TxLAPD

Enable

R/W

0001

000

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