XRT7250 datasheet(293/463 Pages) EXAR

293 / 463 page

XRT7250

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DS3/E3 FRAMER IC

REV. 1.1.1

274

Setting this bit-field to “1” accomplishes the following.

• It configures the Transmit E3 Framer block to com-

pute the BIP-4 value of a given E3 frame, and insert

in to the very last nibble, within the very next out-

bound E3 frame. (Hence, bits 1533 through 1536,

within each E3 frame, will function as the BIP-4

value)

• It configures the Receive E3 Framer block to com-

pute and verify the BIP-4 value of each incoming

E3 frame.

5.2.4.2.3

Generating Errored E3 Frames

The Transmit E3 Framer block permits the user to in-

sert errors into the framing and error detection over-

head bites (e.g., the FAS pattern, and the BIP-4 nib-

ble) of the outbound E3 data stream in order to sup-

port Remote Terminal Equipment testing. The user

can exercise this option by writing data into any of the

following registers.

• TxE3 FAS Error Mask Register - 0

• TxE3 FAS Error Mask Register - 1

• TxE3 BIP-4 Error Mask Register

Inserting Errors into the FAS pattern of the out-

bound’ E3 frames.

The user can insert errors into the FAS pattern bits, of

each outbound E3 frame, by writing the appropriate

data into either the TxE3 FAS Error Mask Register - 0

or TxE3 FAS Error Mask Register - 1.

As the Transmit E3 Framer block formulates the out-

bound E3 frames, the contents of the FAS pattern bits

are automatically XORed with the contents of these

two registers. The results of this XOR operation is

written back into the corresponding bit-field within the

outbound E3 frame, and is transmitted to the Remote

Terminal Equipment. Therefore, if the user does not

wish to modify any of these bits, then these registers

must contain all “0’s” (the default value).

Inserting Errors into the BIP-4 nibble, within each

outbound E3 frame.

The user can insert errors into the BIP-4 nibble, within

each outbound E3 frame, by writing the appropriate

data into the TxE3 BIP-4 Error Mask Register.

TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)

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

BIP-4

Enable

TxASourceSel[1:0]

TxNSourceSel[1:0]

Tx AIS

Enable

Tx LOS

Enable

Tx FAS

Source

Select

R/W

XXXX

TXE3 FAS ERROR MASK REGISTER - 0 (ADDRESS = 0X48)

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

Not Used

TxFAS_Error_Mask_Upper[4:0]

R/W

XXX

TXE3 FAS ERROR MASK REGISTER - 1 (ADDRESS = 0X49)

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

Not Used

TxFAS_Error_Mask_Lower[4:0]

R/W

XXX

XRT7250 Datasheet(PDF) 293 Page - Exar Corporation

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