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XRT79L71
PRELIMINARY
15
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
The Receive Trail-Trace Message Controller Block (ITU-T G.832 Applications Only)
The Receive FEAC Controller Block (DS3, C-bit Parity Applications Only)
The Receive ATM Cell Processor Block
The Receive Overhead Data Output Interface Block
The Receive UTOPIA Interface Block
Each of these functional blocks is briefly discussed below.
These functional blocks will be discussed in
considerable detail throughout this data sheet.
1.3.1
The Transmit UTOPIA Interface Block
The purpose of the Transmit UTOPIA Interface block is to provide a standard UTOPIA Level 1, 2 or 3 interface
to the ATM Layer Processor, for writing in the contents of all Valid ATM cells, into the Transmit FIFO (TxFIFO).
The Transmit UTOPIA Interface Block can be configured to operate with either an 8 or 16-bit wide Transmit
UTOPIA Data bus.
NOTE:
The Transmit UTOPIA Interface block supports UTOPIA Level 3 from a signaling stand-point.
The Transmit
UTOPIA Interface Block (within the XRT79L71) still only supports a 16-bit wide (not 32-bit wide) UTOPIA Bus and
only operates at clock rates of up to 50MHz (not 100MHz).
1.3.2
The Transmit Overhead Data Input Interface block (not shown in Figure 4) The purpose of the Transmit Overhead Data Input Interface block is to permit the user to externally insert their
own values for overheads bits into the outbound DS3/E3 data-stream.
The Transmit ATM Cell Processor Block
The purpose of the Transmit ATM Cell Processor block is to read out the contents of user cells that have been
written into the TxFIFO (via the Transmit UTOPIA Interface block); and perform the following functions.
Optionally Compute and Verify the HEC byte of each cell written into the TxFIFO
To optionally discard all incoming ATM cells that contain HEC byte errors
To optionally compute and insert the HEC byte into the fifth octet position, within each ATM cell that is written
into the TxFIFO
To optionally filter User Cells (that are read out from the TxFIFO) by either discarding these User Cells, or by
replicating them and routing the copies of these cells to the Transmit Cell Extraction Buffer
To insert cells (residing within the Transmit Cell Insertion Buffer) into the Transmit Data Path anytime the
TxFIFO is depleted of user cells
To generate Idle Cells anytime the TxFIFO and the Transmit Cell Insertion Buffer are depleted of User cells
To route the composite stream of valid and idle cells to either the Transmit PLCP Processor or the Transmit
DS3/E3 Framer Block.
1.3.3
The Transmit FEAC Controller Block (DS3, C-bit Parity 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.
NOTE: The Transmit FEAC Controller block is only active if the XRT79L71 is configured to operate in the DS3, C-bit Parity
Framing format.
1.3.4
The Transmit Trail-Trace Message Controller Block (E3, ITU-T G.832 Applications Only)
The purpose of the Transmit Trail-Trace Message Controller block is to permit a given terminal equipment to
repeatedly transmit a "Trail-Trace" Message to the remote terminal equipment, via the TR bytes within each
outbound E3, ITU-T G.832 frame.
1.3.5
The Transmit SSM Controller Block (E3, ITU-T G.832 Applications Only)