XRT7250 datasheet(25/463 Pages) EXAR

25 / 463 page

XRT7250

DS3/E3 FRAMER IC

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REV. 1.1.1

I/O

Bi-directional Data Bus (Microprocessor Interface Section):

Please see description for D7, pin 39

I/O

MSB of Bi-Directional Data Bus (Microprocessor Interface Sec-

tion):

This pin, along with pins D0 - D6, function as the Microprocessor Interface bi-

directional data bus, and is intended to be interfaced to the "local" microproces-

sor.

VDD

****

Power Supply Pin

TxFrameRef

Transmit Framer Reference Input:

This input pin functions as the "Transmit Frame Generation" reference signal, if

the XRT7250 has been configured to operate in the "Local-Time/Frame Slave"

Mode. If the XRT7250 has been configured to operate in the "Local-Time/

Frame-Slave" Mode, then the user's terminal equipment is expected to apply a

pulse (to this input pin) once every 106.4 microseconds (for DS3 applications);

once every 125 microseconds (for E3, ITU-T G.832 applications) or once every

44.7 microseconds (for E3, ITU-T G.751 applications).

In the "Local-Time/Frame-Slave" Mode, the Transmit Section of the XRT7250

Framer IC will initiate its generation of a new "outbound" DS3 or E3 frame,

upon the rising edge of this signal.

NOTE: The user can configure the XRT7250 Framer IC to operate in the "Local

Time/Frame Slave" Mode by writing "xxxx xx01" into the "Framer Operating

Mode" Register (Address = 0x00).

GND

****

Ground Pin

TxInClk

Transmit Framer Reference Clock Input.

This input pin functions as the "Timing Reference" for the Transmit Section of

the XRT7250 Framer IC; if the device has been configured to operate in the

"Local-Time" Mode. Further, if the XRT7250 Framer IC has been configured to

operate in the "Local-Time" Mode, the "Transmit Payload Data Input Interface

will sample the data at the TxSer input pin, upon the rising edge of "TxInClk".

For E3 applications, the user should apply a 34.368MHz clock signal. For DS3

applications, the user should apply a 44.736MHz clock signal.

The user can configure the XRT7250 Framer IC to operate in the "Local-Time"

mode by writing "xxxx xx01" or "xxxx xx1x" into the "Framer Operating Mode"

TxAISEn

Transmit AIS Command Input

Setting this input pin "high" configures the Transmit Section to generate and

transmit an AIS Pattern.

Setting this input pin "low" configures the Transmit Section to generate E3 or

DS3 traffic in a normal manner.

PIN DESCRIPTION

PIN #NAME

TYPE

DESCRIPTION

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