XRT7250 datasheet(242/463 Pages) EXAR

242 / 463 page

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DS3/E3 FRAMER IC

XRT7250

REV. 1.1.1

223

• It will set Bit 6 (LOS Interrupt Status) within the

RxDS3 Interrupt Status register to “1”, as illustrated

below.

Whenever the user’s system encounters the Change

of LOS on Receive Interrupt, then it should do the fol-

lowing.

1. It should determine the current state of the LOS

condition. Recall, that this interrupt can gener-

ated, whenever the XRT7250 Framer declares or

clears the LOS defects. Hence, the user can

determine the current state of the LOS defect by

reading the state of Bit 6 (RxLOS), within the

RxDS3 Configuration & Status Registers, as illus-

trated below.

If the LOS State is TRUE

1. It should transmit a FERF (Far-End Receive Fail-

ure) to the Remote Terminal Equipment. The

XRT7250 Framer IC automatically supports this

action via the FERF-upon-LOS feature.

2. It should transmit the appropriate FEAC Message

(per Bellcore GR-499-CORE), to the Remote Ter-

minal, indicating that a Loss of Signal condition

has been declared.

If the LOS State is FALSE

1. It should cease transmitting a FERF indicator to

the Remote Terminal Equipment. The XRT7250

Framer IC automatically supports this action via

the FERF-upon-LOS feature.

2. It should transmit the appropriate FEAC Message

(per Bellcore GR-499-CORE), to the Remote Ter-

minal Equipment, indicating that the Loss of Sig-

nal condition has been cleared.

4.3.6.2.2

The Change of State on Receive OOF

Interrupt

If the Change of State on Receive OOF (Out-of-

Frame) Interrupt is enabled, then the XRT7250 Fram-

er IC will generate an interrupt in response to either of

the following conditions.

1. When the XRT7250 Framer IC declares an OOF

(Out of Frame) condition, and

2. When the XRT7250 Framer IC clears the OOF

(Out of Frame) condition.

Conditions causing the XRT7250 Framer IC to de-

clare an OOF condition

• If the Receive DS3 Framer block (within the

XRT7250 Framer IC) detects at least either 3 or 6

F-bit errors, in the last 16 F-bits.

Conditions causing the XRT7250 Framer IC to

clear the OOF condition.

• Whenever, the Receive DS3 Framer block transi-

tions from the M-Bit Search into the In-Frame state

(within the Frame Acquisition/Maintenance State

Machine Diagram).

Enabling and Disabling the Change of State on

Receive OOF Interrupt:

The user can enable or disable the Change of State

on Receive OOF Interrupt, by writing the appropriate

RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)

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

CP-Bit Error

Interrupt

Status

LOS

Interrupt

Status

AIS

Interrupt

Status

Idle Interrupt

Status

FERF

Interrupt

Status

AIC

Interrupt

Status

OOF

Interrupt

Status

P-Bit Error

Interrupt

Status

RUR

1000

000

RXDS3 CONFIGURATION & STATUS REGISTER (ADDRESS = 0X10)

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

RxAIS

RxLOS

RxIdle

RxOOF

Reserved

Framing On

Parity

FSync

Algo

MSync

Algo

RUR

1000

000

XRT7250 Datasheet(PDF) 242 Page - Exar Corporation

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