XRT79L71IB datasheet(64/109 Pages) EXAR

64 / 109 page

XRT79L71

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

REV. 1.0.0

• The Transmit High-Speed HDLC Controller Block

• The Transmit LAPD Controller Block

• The Transmit FEAC Controller Block (DS3 Applications only)

• The Transmit Trail-Trace Message Controller Block (E3, ITU-T G.832 Applications only)

• The Transmit SSM Controller Block (E3, ITU-T G.832 Applications only)

• The Transmit DS3/E3 Framer Block

• The Transmit DS3/E3 LIU Block

• The Receive DS3/E3 LIU Block

• The Receive DS3/E3 Framer Block

• The Receive Trail-Trace Message Controller Block (E3, ITU-T G.832 Applications only)

• The Receive SSM Controller Block (E3, ITU-T G.832 Applications only)

• The Receive FEAC Controller Block (DS3 Applications only)

• The Receive LAPD Controller Block

• The Receive High-Speed HDLC Controller Block

Each of these functional blocks is briefly discussed below. These functional blocks will also be discussed in

considerable detail throughout this data sheet.

The Transmit High-Speed HDLC Controller Block

The purpose of the Transmit High-Speed HDLC Controller block is to perform the following tasks.

• To accept user payload data, in a byte-wide manner (via an 8-bit wide Input Data Bus)

• To (while accepting this user payload data, via this byte-wide interface, encapsulate this user data into an

HDLC frame)

• To generate and transmit a repeating string of Flag Sequence octets (0x7E), whenever the Transmit High-

Speed HDLC Controller block is not accepting nor processing user data

• To route these outbound HDLC frames and Flag Sequence octets to the Transmit DS3/E3 Framer block for

further processing.

NOTES:

Whenever the XRT79L71 has been configured to operate in the High-Speed HDLC Controller Mode, then the role

of the Transmit Payload Data Input Interface block will be replaced by the Transmit High-Speed HDLC Controller

block.

The Transmit High Speed HDLC Controller block should NOT be confused with the Transmit LAPD Controller

block (which also exists within the XRT79L71).

The Transmit Overhead Data Input Interface block (not shown in Figure 3)

If the XRT79L71 has been configured to operate in the High-Speed HDLC Controller Mode, then the Transmit

Overhead Data Input Interface block will be disabled.

The Transmit LAPD Controller Block

The purpose of the Transmit LAPD Controller block is to permit the user to transmit LAPD/PMDL (Path

Maintenance Data Link) Messages to the remote terminal equipment. The Transmit LAPD Controller block

comes with a LAPD Controller/Transmitter (not to be confused with the Transmit High-Speed HDLC Controller)

and 90 bytes of on-chip RAM (for storage of outbound PMDL Messages) prior to transmission.

The Transmit FEAC Controller Block (DS3 Applications only)

The purpose of the Transmit FEAC Controller block is to permit the user to transmit FEAC (Far-End Alarm &

Control) Messages to the remote terminal equipment.

XRT79L71IB Datasheet(PDF) 64 Page - Exar Corporation

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