XRT7250 datasheet(129/463 Pages) EXAR

129 / 463 page

XRT7250

DS3/E3 FRAMER IC

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REV. 1.1.1

110

This Read-Only register, along with the Frame CP-Bit

Error - One-Second Accumulator Register - MSB (Ad-

dress = 0x72) contains a 16-bit representation of the

number of CP Bit Errors tjhat have been detected by

the Receive DS3/E3 Framer block, within the last

one-second sampling period. This register contains

the LSB (or Lower Byte) value of this 16-bit expres-

sion.

2.3.8.19 Line Interface Drive Register

Bit 5 - REQB - (Receive Equalization Bypass Con-

trol)

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

state of the REQB output pin of the UNI device. This

output pin is intended to be connected to EITHER OF

the REQB input pins of the XRT7300 DS3/E3 LIU IC.

If the user forces this signal to toggle "High", then the

Receive Equalizer (within the XRT7300 device) will

be disabled. Conversely, if the user forces this signal

to toggle "Low", then the Receive Equalizer (within

the XRT7300 device) will be enabled.

Writing a "1" to this bit-field causes the Framer device

to toggle the REQB output pin "High". Writing a "0" to

this bit-field causes the Framer device to toggle the

REQB output pin "Low".

For information on the criteria that should be used

when deciding whether to bypass the equalization cir-

cuitry or not, please consult the XRT7300 DS3/E3/

STS-1 LIU IC data sheet.

NOTE: If the customer is not using the XRT7300 DS3/E3/

STS-1 LIU IC, then this bit-field and the REQB output pin

can be used for other purposes.

Bit 4 - TAOS - (Transmit All Ones Signal)

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

state of the TAOS output pin of the UNI device. This

output pin is intended to be connected to the TAOS

input pin of the XRT7300 DS3/E3/STS-1 LIU IC. If

the user forces this signal to toggle "High", then the

XRT7300 LIU device will transmit an "All Ones" pat-

tern onto the line. Conversely, if the user commands

this output signal to toggle "Low" then the XRT7300

LIU IC will proceed to transmit data based upon the

pattern that it receives via the TxPOS and TxNEG

output pins (of the Framer IC).

Writing a "1" to this bit-field will cause the TAOS out-

put pin to toggle "High". Writing a "0" to this bit-field

will cause this output pin to toggle "Low".

NOTE: If the customer is not using the XRT7300 DS3/E3/

STS-1 LIU IC, then this bit-field, and the TAOS output pin

can be used for other purposes.

Bit 3 - Encodis - (B3ZS Encoder Disable)

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

state of the Encodis output pin of the UNI device.

This output pin is intended to be connected to the En-

codis input pin of the XRT7300 DS3/E3/STS-1 LIU

IC. If the user forces this signal to toggle "High", then

the internal B3ZS/HDB3 encoder (within the

XRT7300 device) will be disabled. Conversely, if the

user command this output signal to toggle "Low",

then the internal B3ZS/HDB3 encoder (within the

XRT7300 device) will be enabled.

Writing a "1" to this bit-field causes the Framer IC to

toggle the Encodis output pin "High". Writing a "0" to

this bit-field will cause the Framer IC to toggle this

output pin "Low".

NOTES:

1. The B3ZS/HDB3 encoder, within the XRT7300

device, is not to be confused with the B3ZS/HDB3

encoding capable that exists within the Transmit

Section of the Framer IC.

2. The user is advised to disabled the B3ZS/HDB3

encoder (within the XRT7300 IC) if the XRT7250 is

configured to operate in the B3ZS/HDB3 line code.

3. If the customer is not using the XRT7300 DS3/E3/

STS-1 LIU IC, then this bit-field and the Encodis

output pin can be used for other purposes.

4. It is permissible to tie the Encodis output pin of the

XRT7250 Framer IC to both the Encodis and Deco-

dis input pins of the XRT7300 device.

Bit 2 - TxLev - (Transmit Output Line Build-Out

Select Output)

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

state of the TxLev output pin of the Framer device.

This output pin is intended to be connected to the Tx-

Lev input pin of the XRT7300 DS3/E3/STS-1 LIU IC.

If the user commands this signal to toggle High, then

the XRT7300 DS3/E3/STS-1 LIU IC will disable the

LINE INTERFACE DRIVE REGISTER (ADDRESS = 0X80)

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

REQB

TAOS

ENCODIS

TxLEV

RLOOP

LLOOP

R/W

001

000

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