XRT7250 datasheet(313/463 Pages) EXAR

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XRT7250

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DS3/E3 FRAMER IC

REV. 1.1.1

294

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 signal (FAS pattern) is

present, and at its proper location. 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 an invalid FAS pattern in four

consecutive frames.

Since the Receive E3 Framer block requires the de-

tection of an invalid FAS pattern in four consecutive

frames, in order for it to transition to the OOF Condi-

tion 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 FAS pattern, it will incre-

ment the PMON Framing Error Event Count Regis-

ters (Address = 0x52 and 0x53). The bit-format for

these two registers are depicted below.

5.3.2.3

Forcing a Reframe via Software Com-

mand

The XRT7250 Framer IC permits the user to com-

mand a reframe procedure with the Receive E3 Fram-

er block via software command. If the user writes a

“1” into Bit 0 (Reframe) within the I/O Control Register

(Address = 0x01), as depicted below, then the Re-

ceive E3 Framer block will be forced into the FAS Pat-

tern Search state, per Figure 138., and will begin its

search for the FAS Pattern.

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

000

111

PMON FRAMING BIT/BYTE ERROR COUNT REGISTER - MSB (ADDRESS = 0X52)

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

Framing Bit/Byte Error Count - High Byte

RURRUR

RUR

RURRUR

000

PMON FRAMING BIT/BYTE ERROR COUNT REGISTER - LSB (ADDRESS = 0X53)

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

Framing Bit/Byte Error Count - Low Byte

RURRUR

RUR

RURRUR

000

XRT7250 Datasheet(PDF) 313 Page - Exar Corporation

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