XRT7250 datasheet(210/463 Pages) EXAR

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DS3/E3 FRAMER IC

XRT7250

REV. 1.1.1

191

Table 38 relates the contents of this bit-field to the

OOF Declaration criteria

NOTE: Once the Receive DS3 Framer block has declared

an OOF condition, it will transition back to the F-Bit Search

state within the DS3 Frame Acquisition/Maintenance algo-

rithm (per Figure 81).

In addition to selecting an OOF Declaration criteria

for the F-bits, the user has the following options for

configuring the OOF Declaration criteria based upon

M-bits.

1. M-bit errors do not cause a OOF Declaration, or

2. OOF will be declared if 3 out of 4 consecutive M-

bits are in error.

The user will select between these two options by

writing the appropriate value to Bit 0 (M-Sync Algo)

within the Receive DS3 Configuration and Status

Table 39 relates the contents of this Bit Field to the M-

Bit Error criteria for Declaration of OOF.

The Framing on Parity Criteria for OOF Declara-

tion

Finally, the Framer IC offers the Framing on Parity op-

tion, which also effects the OOF Declaration criteria.

As was mentioned earlier, the Framer IC allows the

user to configure the Receive DS3 Framer block to

detect 'valid-parity' before declaring itself In-Frame.

This same selection also configures the Receive DS3

Framer block to also declare an OOF Condition if a P-

bit error is detected in 2 of the last 5 M-frames.

RX DS3 CONFIGURATION AND STATUS REGISTER, (ADDRESS = 0X10)

BIT 7BIT 6BIT 5BIT 4BIT 3BIT2

BIT 1BIT 0

RxAIS

RxLOS

RxIdle

RxOOF

Int LOS

Disable

Framing on

Parity

F-Sync Algo

M-Sync Algo

R/W

XXXX

TABLE 38: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 1 (F-SYNC ALGO) WITHIN THE RX DS3

CONFIGURATION AND STATUS REGISTER, AND THE RESULTING F-BIT OOF DECLARATION CRITERIA USED BY THE

RECEIVE DS3 FRAMER BLOCK

F-SYNC ALGO (BIT 1)

OOF DECLARATION CRITERIA

OOF is declared when 6 out of 16 consecutive F-bits are in error.

OOF is declared when 3 out of 16 consecutive F-bits are in error.

RX DS3 CONFIGURATION AND STATUS REGISTER, (ADDRESS = 0X10)

BIT 7BIT 6BIT 5BIT 4BIT 3BIT2BIT 1

BIT 0

RxAIS

RxLOS

RxIdle

RxOOF

Int LOS

Disable

Framing on

Parity

F-Sync Algo

M-Sync Algo

R/W

XXXX

TABLE 39: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 0 (M-SYNC ALGO) WITHIN THE RX DS3

CONFIGURATION AND STATUS REGISTER, AND THE RESULTING M-BIT OOF DECLARATION CRITERIA USED BY THE

RECEIVE DS3 FRAMER BLOCK

MSYNC ALGO

OOF DECLARATION CRITERIA

M-Bit Errors do not result in the declaration of OOF

OOF is declared when 3 out of 4 M-bits are in error.

XRT7250 Datasheet(PDF) 210 Page - Exar Corporation

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