XRT7250 datasheet(299/463 Pages) EXAR

299 / 463 page

XRT7250

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DS3/E3 FRAMER IC

REV. 1.1.1

280

Table 57 relates the content of this bit-field to the Bi-

polar Line Code that E3 Data will be transmitted and

received at.

NOTES:

1. This bit is ignored if the Unipolar mode is selected.

2. This selection also effects the operation of the

Receive E3 LIU Interface block

5.2.5.2

TxLineClk Clock Edge Selection

The Framer also allows the user to specify whether

the E3 output data (via TxPOS and/or TxNEG output

pins) is to be updated on the rising or falling edges of

the TxLineClk signal. This selection is made by writ-

ing to bit 2 of the I/O Control Register, as depicted be-

low.

Table 58 relates the contents of this bit field to the

clock edge of TxClk that E3 Data is output on the Tx-

POS and/or TxNEG output pins.

NOTE: The user will typically make the selection based

upon the set-up and hold time requirements of the Transmit

LIU IC.

I/O CONTROL REGISTER (ADDRESS = 0X01)

BIT 7BIT 6BIT 5

BIT 4BIT 3BIT2BIT 1BIT 0

Disable TxLOC

LOC

Disable

RxLOC

AMI/ZeroSup*

Unipolar/

Bipolar*

TxLine CLK

Invert

RxLine CLK

Invert

Reframe

R/W

R/WR/W

R/W

000

TABLE 57: THE RELATIONSHIP BETWEEN BIT 4 (AMI/

HDB3*) WITHIN THE I/O CONTROL REGISTER AND THE

BIPOLAR LINE CODE THAT IS OUTPUT BY THE TRANSMIT

E3 LIU INTERFACE BLOCK

BIT 4BIPOLAR LINE CODE

HDB3

AMI

II/O CONTROL REGISTER (ADDRESS = 0X01)

BIT 7BIT 6BIT 5BIT 4BIT 3

BIT2BIT 1BIT 0

Disable TxLOC

LOC

Disable

RxLOC

AMI/ZeroSup*

Unipolar/

Bipolar*

TxLine CLK

Invert

RxLine CLK

Invert

Reframe

R/W

100

000

TABLE 58: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (TXLINECLK INV) WITHIN THE I/O CONTROL

BIT 2RESULT

Rising Edge:

Outputs on TxPOS and/or TxNEG are updated on the rising edge of TxLineClk.

See Figure 125 for timing relationship between TxLineClk, TxPOS and TxNEG signals, for this selection.

Falling Edge:

Outputs on TxPOS and/or TxNEG are updated on the falling edge of TxLineClk.

See Figure 126 for timing relationship between TxLineClk, TxPOS and TxNEG signals, for this selection.

XRT7250 Datasheet(PDF) 299 Page - Exar Corporation

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