XRT7250 datasheet(341/463 Pages) EXAR

341 / 463 page

XRT7250

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DS3/E3 FRAMER IC

REV. 1.1.1

322

Setting this bit-field to “1” enables the Receive Sec-

tion at the Block Level) for interrupt generation. Con-

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

ceive Section for interrupt generation.

5.3.6.2

Enabling/Disabling and Servicing Inter-

rupts

As mentioned previously, the Receive Section of the

XRT7250 Framer IC contains numerous interrupts.

The Enabling/Disabling and Servicing of each of

these interrupts is described below.

5.3.6.2.1

The Change in Receive LOS Condi-

tion Interrupt

If the Change in Receive LOS 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 LOS

(Loss of Signal) Condition, and

2. When the XRT7250 Framer IC clears the LOS

condition.

Conditions causing the XRT7250 Framer IC to de-

clare an LOS Condition.

• If the XRT7300 LIU IC declares an LOS condition,

and drives the RLOS input pin (of the XRT7250

Framer IC) “High”.

• If the XRT7250 Framer IC detects 32 consecutive

“0”, via the RxPOS and RxNEG input pins.

Conditions causing the XRT7250 Framer IC to

clear the LOS Condition.

• If the XRT7300 LIU IC clears the LOS condition and

drives the RLOS input pin (of the XRT7250 Framer

IC) “Low”.

• If the XRT7250 Framer IC detects a string of 32

consecutive bits (via the RxPOS and RxNEG input

pins) that does NOT contain a string of 4 consecu-

tive “0’s”.

Enabling and Disabling the Change in Receive

LOS Condition Interrupt

The user can enable or disable the Change in Re-

ceive LOS Condition Interrupt, by writing the appro-

priate value into Bit 1 (LOS Interrupt Enable), within

the RxE3 Interrupt Enable Register - 1, as indicated

below.

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 LOS 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 1 (LOS Interrupt Status), within the Rx

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

below.

BLOCK INTERRUPT ENABLE REGISTER (ADDRESS = 0X04)

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

RxDS3/E3

Interrupt

Enable

Not Used

TxDS3/E3

Interrupt

Enable

One-Second

Interrupt

Enable

R/W

RORO

R/W

000

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

000

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