xrt94l33 Exar Corporation, xrt94l33 Datasheet - Page 172

• Manufacturer Part Number: xrt94l33
• Description: Multi-channel, Multi-function Device Aggregates 3 Ds3/e3/sts-1 Into Oc3/stm-1
• Manufacturer: Exar Corporation

XRT94L33
Rev.1.2.0.
Figure 20 presents a simple block diagram of the Transmit ATM Cell Processor block (with the external pins
indicated).
Figure 20: Simple Illustration of the Transmit ATM Cell Processor Block and the Associated External
Pins
A very brief description of the Transmit ATM Cell Processor block
The Transmit ATM Cell Processor block reads in ATM cells from the Transmit UTOPIA FIFO (TxFIFO) within
the Transmit UTOPIA Interface block. Immediately after reading in a given cell from the TxFIFO, the Transmit
ATM Cell Processor will compute and verify the parity value of each byte or (16-bit) word of this ATM cell. If
the Transmit ATM Cell Processor block detects a parity error within one of these bytes then (or 16-bit words)
then the entire cell will be (optionally) discarded. Afterwards, each ATM cell (which is not discarded due to
parity error) will be processed through a “user-configurable” filter. If the cell does not meet the “user-cell”
filtering criteria, then it will be discarded. Next, the ATM cell will be processed through both the “Transmit
Data Path” and the “Transmit Cell Extraction” Processor, in parallel. The manner in which this ATM cell is
handled (via each of these paths) is briefly described below.
2.2.3
The User Cell Filter blocks (within the Transmit ATM Cell Processor block) permit the user to configure it to
copy (e.g., replicate) certain ATM cells; and route these “copies” of ATM cells to the “Transmit Cell Extraction
Buffer”. The “Transmit Cell Extraction Processor permits the user to read out the contents of these “copied”
ATM cells via the Microprocessor Interface.
T
HE
T
RANSMIT
TxGFCMSB
TxCellTxed
TxGFCClk
C
TxGFC
ELL
E
XTRACTION
3-CHANNEL DS3/E3/STS-1 TO STS-3/STM-1 MAPPER IC DATA SHEET
P
ROCESSOR
To Transmit STS-3c/STS-12c
172
From Transmit UTOPIA
POH Processor Block
Transmit ATM
Interface Block
Processor
Block
Cell
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