XRT7250 datasheet(344/463 Pages) EXAR

344 / 463 page

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XRT7250

DS3/E3 FRAMER IC

REV. 1.1.1

325

5.3.6.2.3

The Change in Receive LOF Condi-

tion Interrupt

If the Change in Receive LOF Condition Interrupt is

enabled, then the XRT7250 Framer IC will generate

an interrupt in response to either of the following con-

ditions.

1. When the XRT7250 Framer IC declares an LOF

(Out of Frame) Condition, and

2. When the XRT7250 Framer IC clears the LOF

condition.

Conditions causing the XRT7250 Framer IC to de-

clare an LOF Condition.

• If the Receive E3 Framer block (within the XRT7250

Framer IC) detects Framing Bit errors, within four

consecutive incoming E3 frames, and is not capa-

ble of transition back into the In-Frame state within

a 1ms or 3ms period.

Conditions causing the XRT7250 Framer IC to

clear the LOF Condition.

• If the Receive E3 Framer block transitions from the

OOF Condition state to the LOF Condition state

(see Figure 115).

• If the Receive E3 Framer block transitions back into

the In-Frame state.

Enabling and Disabling the Change in Receive

LOF Condition Interrupt

The user can enable or disable the Change in Re-

ceive LOF Condition Interrupt, by writing the appropri-

ate value into Bit 3 (LOF Interrupt Enable), within the

RxE3 Interrupt Enable Register - 1, as indicated be-

low.

Setting this bit-field to “1” enables this interrupt. Con-

versely, setting this bit-field to “0” disables this inter-

rupt.

Servicing the Change in Receive LOF Condition

Interrupt

Whenever the XRT7250 Framer IC detects this inter-

rupt, it will do all of the following.

• It will assert the Interrupt Request output pin (INT),

by driving it “Low”.

• It will set Bit 6 (LOF Interrupt Status), within the Rx

E3 Interrupt Status Register - 1 to “1”, as indicated

below.

5.3.6.2.4

The Change in Receive AIS Condition

Interrupt

If the Change in Receive AIS Condition Interrupt is

enabled, then the XRT7250 Framer IC will generate

an interrupt in response to either of the following con-

ditions.

1. When the XRT7250 Framer IC declares an AIS

(Loss of Signal) Condition, and

2. When the XRT7250 Framer IC clears the AIS

condition.

Conditions causing the XRT7250 Framer IC to de-

clare an AIS Condition.

• If the XRT7250 Framer IC detects 7 or less “0”

within 2 consecutive E3 frames.

Conditions causing the XRT7250 Framer IC to

clear the AIS Condition.

RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)

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

Not Used

COFA

Interrupt

Enable

OOF

Interrupt

Enable

LOF

Interrupt

Enable

LOS

Interrupt

Enable

AIS

Interrupt

Enable

R/W

0000

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

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

RxLOF

Algo

RxLOF

RxOOF

RxLOS

RxAIS

Not Used

RxFERF

R/W

RORO

RORORORO

1100

111

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