XRT79L71IB datasheet(37/109 Pages) EXAR

37 / 109 page

XRT79L71

REV. 1.0.0

1-CHANNEL DS3/E3 ATM UNI/PPP/CLEAR-CHANNEL FRAMER IC - HARDWARE

RxRED/

RxNib_3/

RxHDLCDat_3

Receive Section Red Alarm Indicator/Receive Nibble Interface Output pin -

Bit 3/Receive HDLC Controller Data Bus output pin - Bit 3:

The function of this output pin depends upon whether the XRT79L71 has been

configured to operate in the Clear-Channel Framer/Nibble-Parallel Mode, the

High-Speed HDLC Controller Mode, or in some other mode.

Clear-Channel Framer/Nibble-Parallel Mode - RxNib_3:

The XRT79L71 will output Received data from the remote terminal equipment

to the System-Side terminal equipment via this pin, along with RxNib_0 through

RxNib_2. This particular output pin functions as the LSB. The data at this pin is

updated on the rising edge of the RxClk output signal. Hence, the user's Sys-

tem-Side terminal equipment should sample this signal upon the falling edge of

RxClk.

High-Speed HDLC Controller Mode - Receive High-Speed HDLC Controller

Output Interface Block - Data Bus Output Pin #3 - RxHDLCDat_3:

This output pin along with RxHDLCDat_[7:4] and RxHDLCDat_[2:0] functions

as the Receive High-Speed HDLC Controller Output Interface byte wide output

data bus. The Receive High-Speed HDLC Controller Output Interface block will

output the contents of all HDLC frames and flag sequence octects via this out-

put data bus, upon the rising edge of the RxHDLCClk output signal. Hence, the

user's local terminal equipment should be designed/configured to sample this

data upon the falling edge of the RxHDLCClk output clock signal.

Other Modes - RxRED - RED Alarm/Defect Indicator Output pin:

The XRT79L71 will assert this output pin (e.g., toggle it "High") in order to indi-

cate that the Receive DS3/E3 Framer block is currently declaring at least one of

the following defect conditions.

• LOS - Loss of Signal Defect Condition

• OOF - Out of Frame Defect Condition

• AIS - Alarm Indication Signal Defect Condition.

The XRT79L71 will negate this output pin (e.g., toggle it "Low") anytime that the

Receive DS3/E3 Framer block is NOT currently declaring any of the above-

mentioned defect conditions.

PIN #NAME

TYPE

DESCRIPTION

XRT79L71IB Datasheet(PDF) 37 Page - Exar Corporation