XRT7250 datasheet(414/463 Pages) EXAR

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XRT7250

DS3/E3 FRAMER IC

REV. 1.1.1

395

Finally, the Receive E3 Framer block will also inform

the external circuitry of this transition to the LOF Con-

dition state by toggling the RxLOF output pin “High”.

6.3.2.2

The Framing Maintenance Mode

Once the Receive E3 Framer block enters the In-

Frame state, then it will notify the Microprocessor/Mi-

crocontroller of this fact by generating both the

Change in OOF Condition and Change in LOF Condi-

tion Interrupts. When this happens, bits 2 and 3 (LOF

Interrupt Status and OOF Interrupt Status) will be set

to “1”, as depicted below.

Additionally, the Receive E3 Framer block will inform

the external circuitry of its transition to the In-Frame

state by toggling both the RxOOF and RxLOF output

pins "Low”.

Finally, the Receive E3 Framer block will negate both

the RxOOF and the RxLOF bit-fields within the Rx E3

Configuration & Status Register, as depicted below.

When the Receive E3 Framer block is operating in the

In-Frame state, it will then begin to perform Frame

Maintenance operations, where it will continue to ver-

ify that the Frame Alignment octets (FA1, FA2) are

present, at their proper locations. While the Receive

E3 Framer block is operating in the Frame Mainte-

nance Mode, it will declare an Out-of-Frame (OOF)

Condition if it detects invalid Framing Alignment bytes

in four consecutive frames.

Since the Receive E3 Framer block requires the de-

tection of invalid Frame Alignment bytes in four con-

secutive frames, in order for it to transition to the OOF

Condition state, it can tolerate some errors in the

Framing Alignment bytes, and still remain in the In-

Frame state. However, each time the Receive E3

Framer block detects an error in the Frame Alignment

bytes, it will increment the PMON Framing Error

Event Count Registers (Address = 0x52 and 0x53).

The bit-format for these two registers are depicted be-

low.

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

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

0001

100

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

1100

000

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