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XRT7300IV

E3/DS3/STS-1 LINE INTERFACE UNIT

Exar Corporation 

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PIN DESCRIPTION

PIN #

SYMBOL

16

STS-1/DS3

17

E3

18

HOST/HW

19

SDI/

(LOSMUTEN)

XRT7300

E3/DS3/STS-1 LINE INTERFACE UNIT

REV. 1.1.1

TYPE

I

I

I

I

DESCRIPTION

STS-1/DS3 Select Input:

A “High” on this pin configures the Clock Recovery Phase Locked Loop to set its

VCO Center frequency to around 51.84 MHz (optimal for SONET STS-1 opera-

tions). A “Low” on this pin configures the Clock Recovery Phase Locked Loop to

set its VCO Center frequency to around 44.736 MHz (optimal for DS3 opera-

tions).

NOTES:

1. The XRT7300 ignores this pin if the E3 pin (pin 17) is set to “1”.

2. This input pin is ignored if the XRT7300 is operating in the HOST Mode.

3. Tie this pin to GND if the XRT7300 is going to be operating in the HOST

Mode.

E3 Select Input:

A “High” on this pin configures the XRT7300 to operate in the E3 Mode.

A “Low” on this pin configures the XRT7300 to check the state of the STS-1/DS3

input pin.

NOTES:

1. This input pin is ignored if the XRT7300 is operating in the HOST Mode.

2. Tie this pin to GND if the XRT7300 is going to be operating in the HOST

Mode.

HOST/HW Mode Select:

This input pin is used to enable or disable the Microprocessor Serial Interface

(e.g., consisting of the SDI, SDO, SCLK, CS and REGRESET pins).

Setting this input pin “High” enables the Microprocessor Serial Interface (e.g.

configures the XRT7300 to operate in the HOST Mode). In this mode, the

XRT7300 is configured by writing data into the on-chip Command Registers via

the Microprocessor Serial Interface. When the XRT7300 is operating in the

HOST Mode, it ignores the states of many of the discrete input pins.

Setting this input pin “Low” disables the Microprocessor Serial Interface (e.g.,

configures the XRT7300 to operate in the Hardware Mode). In this mode, many

of the external input control pins are functional.

Serial Data Input for the Microprocessor Serial Interface (HOST Mode) or

MUTE-upon-LOS Enable Input (Hardware Mode):

The function of this input pin depends upon whether the XRT7300 is operating in

the HOST or the Hardware Mode.

Serial Data Input for the Microprocessor Serial Interface (HOST Mode):

This pin is used to read or write data into the Command Registers of the Micro-

processor Serial Interface. The Read/Write bit, the Address Values of the Com-

mand Registers and Data Value to be written during Write Operations are

applied to this pin.

This input is sampled on the rising edge of the SCLK pin (pin 21).

MUTE-upon-LOS Enable Input (Hardware Mode):

When in the Hardware Mode, this input pin is used to configure the XRT7300 to

MUTE the recovered data via the RPOS and RNEG output pins whenever it

declares an LOS condition.

Setting this input pin “High” configures the XRT7300 to automatically pull the

RPOS and RNEG output pins to GND whenever it is declaring an LOS condition,

thereby MUTing the data being output to the Terminal Equipment.

Setting this input pin “Low” configures the XRT7300 to NOT automatically MUTE

the recovered data whenever an LOS condition is declared.

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