XRT74L74 datasheet(21/498 Pages) EXAR

21 / 498 page

XRT74L74

4 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER

PRELIMINARY

REV. P1.1.1

PIN DESCRIPTION

PIN#NAME

TYPE

DESCRIPTION

General Purpose Input and Output Pins

C13

B13

A13

B12

DMO_0

DMO_1

DMO_2

DMO_3

“Drive Monitor Output” Input (from the XRT73L04 LIU IC):

This input pin is intended to be tied to the DMO output pin of the XRT73L04 E3/

DS3/STS-1 LIU IC. The user can determine the state of this input pin by reading

Bit 2 (DMO) within the Line Interface Scan Register (Address = 0x73). If this

input signal is “High”, then it means that the drive monitor circuitry (within the

XRT73L04 LIU IC) has not detected any bipolar signals at the MTIP and MRING

inputs within the last 128 ± 32 bit-periods. If this input signal is “Low”, then it

means that bipolar signals are being detected at the MTIP and MRING input pins

of the XRT73L04 device.

NOTE: If the designer is not using the XRT73L04 E3/DS3/STS-1 LIU IC, then

this input pin can be used for other purposes.

GPIO_0

GPIO_1

GPIO_2

GPIO_3

I/O

General Purpose Input/Output pins:

Each of these pin can be configured to function as either input or output pins. If a

given pin is configured to function as an Input pin, then the state of this input pin

can be monitored by reading Bit X within the "XXX" Register (Address Location =

0xXX, 0xXX).

If a given pin is configured to function as a Output pin, then the state of this out-

put pin can be controlled by writing the appropriate value into Bit X within the

"XXX" Register.

LLOOP_0

LLOOP_1

LLOOP_2

LLOOP_3

Local Loop-back Output Pin (to the XRT73L04 E3/DS3/STS-1 LIU IC):

This output pin is intended to be connected to the LLOOP input pin of the

XRT73L04 LIU IC. This input pin, along with “RLOOP” permits the user to config-

ure the XRT73L04 LIU IC to operate in either of the following three (3) loop-back

modes.

• Analog Local Loop-Back Mode

• Digital Local Loop-Back Mode

• Remote Loop-Back Mode.

For a detailed description on how to configure the XRT73L04 to operate in each

of these loop-back modes, please see Section _.

Writing a “1” to bit 1 of the “Line Interface Drive Register” (Address = 0xXX,

0xXX) will cause this output pin to toggle “High”. Writing a “0” to this bit-field will

cause the RLOOP output to toggle “Low”.

NOTE: If the user is not using the XRT73L04 DS3/E3/STS-1 LIU IC, then this

output pin can be used for other purposes.

XRT74L74 Datasheet(PDF) 21 Page - Exar Corporation

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