XRT7250 datasheet(416/463 Pages) EXAR

416 / 463 page

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XRT7250

DS3/E3 FRAMER IC

REV. 1.1.1

397

plished by periodically reading the PMON Framing

Bit/Byte Error Event Count Registers (Address = 0x52

and 0x53). The byte format of these registers are

presented below.

6.3.2.5

The RxOOF and RxLOF output pin.

The user can roughly determine the current framing

state that the Receive E3 Framer block is operating in

by reading the logic state of the RxOOF and the Rx-

LOF output pins. Table 85 presents the relationship

between the state of the RxOOF and RxLOF output

pins, and the Framing State of the Receive E3 Framer

block.

6.3.2.6

E3 Receive Alarms

6.3.2.6.1

The Loss of Signal (LOS) Alarm

Declaring an LOS Condition

The Receive E3 Framer block will declare a Loss of

Signal (LOS) Condition, when it detects 32 consecu-

tive incoming “0’s” via the RxPOS and RxNEG input

pins or if the ExtLOS input pin (from the XRT7300

DS3/E3/STS-1 LIU IC) is asserted. The Receive E3

Framer block will indicate that it is declaring an LOS

condition by.

• Asserting the RxLOS output pin (e.g., toggling it

“High”).

• Setting Bit 4 (RxLOS) of the Rx E3 Configuration &

Status Register to “1” as depicted below.

• The Receive E3 Framer block will generate a

Change in LOS Condition interrupt request. Upon

generating this interrupt request, the Receive E3

Framer block will assert Bit 1 (LOS Interrupt Status

within the Rx E3 Framer Interrupt Status Register -

1, as depicted below.

Clearing the LOS Condition

The Receive E3 Framer block will clear the LOS con-

dition when it encounters a stream of 32 bits that

does not contain a string of 4 consecutive zeros.

TABLE 85: THE RELATIONSHIP BETWEEN THE LOGIC STATE OF THE RXOOF AND RXLOF OUTPUT PINS, AND THE

FRAMING STATE OF THE RECEIVE E3 FRAMER BLOCK

RXLOF

RXOOF

FRAMING STATE OF THE RECEIVE E3 FRAMER BLOCK

In Frame

OOF Condition (The Receive E3 Framer block is operating in the 3ms OOF period).

Invalid

LOF Condition

RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)

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

Rx LOF Algo

RxLOF

RxOOF

RxLOS

RxAIS

RxPld Unstab

TMark

RxFERF

R/W

RORO

RORORORO

0010

000

RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)

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

Not Used

COFA

Interrupt

Status

OOF

Interrupt

Status

LOF

Interrupt

Status

LOS

Interrupt

Status

AIS

Interrupt

Status

RUR

0000

010

XRT7250 Datasheet(PDF) 416 Page - Exar Corporation

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