XRT72L50 datasheet(21/471 Pages) EXAR

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XRT72L50

SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

REV. 1.2.1

TxNib3/

TxHDLCDat3

Transmit Nibble-Parallel Payload Data Input -3:

The Terminal Equipment is expected to input data, that is intended to be

transmitted to the remote terminal, over an E3 or DS3 transport medium. The

Framer IC will take data, applied to this pin (along with TxNib1, TxNib2, and

TxNib3), and insert it into an outbound E3 or DS3 frame. The XRT72L50 will

sample the data that is at these input pins, upon the rising edge of the TxNib-

Clk signal.

NOTE: This input pin is active only if the Nibble-Parallel Mode has been

selected.

Transmit HDLC Data Input - 3:

This pin accepts bit 3 TxHDLC data when the HDLC controller is turned on.

GND

****

Ground

VDD

****

Power Supply 3.3V + 5%

TxOHClk

Transmit Overhead Clock:

This output signal serves two purposes:

1. The Transmit Overhead Data Input Interface block will provide a rising clock

edge on this signal, one bit-period prior to the start to the instant that the

Transmit Overhead Data Input Interface block is processing an overhead bit.

2. The Transmit Overhead Data Input Interface will sample the data at the

TxOH input pin, on the falling edge of this clock signal (provided that the TxO-

HIns input pin is "High").

NOTE: The Transmit Overhead Data Input Interface block will supply a clock

edge for all overhead bits within the DS3 or E3 frame (via the TxOHClk output

signal). This includes those overhead bits that the Transmit Overhead Data

Input Interface will not accept from the Terminal Equipment.

TxOHIns/

TxHDLCDat4

Transmit Overhead Data Insert Input:

Asserting this input signal (e.g., setting it "High") enables the Transmit Over-

head Data Input Interface to accept overhead data from the Terminal Equip-

ment. In other words, while this input pin is "High", the Transmit Overhead

Data Input Interface will sample the data at the TxOH input pin, on the falling

edge of the TxOHClk output signal.

Conversely, setting this pin "Low" configures the Transmit Overhead Data

Input Interface to NOT sample (e.g., ignore) the data at the TxOH input pin,

on the falling edge of the TxOHClk output signal.

NOTE: If the Terminal Equipment attempts to insert an overhead bit that can-

not be accepted by the Transmit Overhead Data Input Interface (e.g., if the

Terminal Equipment asserts the TxOHIns signal, at a time when one of these

non-insertable overhead bits are being processed); that particular insertion

effort will be ignored.

Transmit HDLC Data Input - 4:

This pin accepts bit 4 TxHDLC data when the HDLC controller is turned on.

PIN DESCRIPTION

PIN #PIN NAME

TYPE

DESCRIPTION

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