XRT79L71IB datasheet(34/441 Pages) EXAR

34 / 441 page

XRT79L71

PRELIMINARY

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REV. P1.0.3

1 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC

TxMod

Transmit PPP Data Bus - Modulo Indicator:

This input pin is used to specify the number of valid packet octets are being

placed on the TxPData[15:0] input pins.

The Link Layer Processor is expected to set this input pin "Low" when both bytes

on the TxPData[15:0] data bus is valid packet data. Conversely, the Link Layer

Processor is expected to set this input pin "High" when only the upper octet has

valid packet data.

NOTES:

This input pin is only active if the XRT79L71 has been configured to

operate in the PPP Mode.

The Link Layer Processor is expected to set this input pin to the

appropriate state, as each 16-bit word is being written into the

TxPData[15:0] data bus.

TxUData_0/

TxPData_0

TxUData_1/

TxPData_1

TxUData_2/

TxPData_2

TxUData_3/

TxPData_3

TxUData_4/

TxPData_4

TxUData_5/

TxPData_5

TxUData_6/

TxPData_6

TxUData_7/

TxPData_7

TxUData_8/

TxPData_8

TxUData_9/

TxPData_9

TxUData_10/

TxPData_10

TxUData_11/

TxPData_11

TxUData_12/

TxPData_12

TxUData_13/

TxPData_13

TxUData_14/

TxPData_14

TxUData_15/

TxPData_15

Transmit UTOPIA Data Bus Inputs/Transmit POS-PHY Data Bus Inputs:

The function of these input pins depends upon whether the XRT79L71 is operat-

ing in the ATM UNI Mode or in the PPP Mode.

ATM UNI Operation - TxUData[15:0]:

These input pins comprise the Transmit UTOPIA Data Bus input pins. When the

ATM Layer Processor wishes to transmit ATM cell data through the XRT72L74

ATM UNI, it must place this data on these pins. The data, on the Transmit UTO-

PIA Data Bus is latched into the Transmit UTOPIA Interface block upon the rising

edge of TxUClk.

PPP Operation - TxPDATA[15:0]

These input pins comprise the Transmit POS-PHY Data Bus input pins. When a

Network Processor wishes to transmit PPP data through the XRT79L71 Framer/

UNI IC, it must place this data on these pins. The data, on the Transmit POS-

PHY Data Bus is latched into the Transmit POS-PHY Interface block upon the ris-

ing edge of TxPClk.

PIN #NAME

TYPE

DESCRIPTION

XRT79L71IB Datasheet(PDF) 34 Page - Exar Corporation

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