![](http://datasheet.mmic.net.cn/Exar-Corporation/XRT94L33IB-L_datasheet_100163/XRT94L33IB-L_387.png)
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XRT94L33
3-CHANNEL DS3/E3/STS-1 TO STS-3/STM-1 MAPPER IC DATA SHEET
Rev.1.2.0.
387
Figure 90 Illustration of the Functional Block Diagram of the XRT94L33 Mapper IC; with the Receive
STS-3c POH Processor block highlighted
Transmit
UTOPIA
Interface
Block
Transmit
UTOPIA
Interface
Block
Receive
UTOPIA/
Interface
Block
Receive
UTOPIA/
Interface
Block
Transmit
ATM
Cell Processor
Block
Transmit
ATM
Cell Processor
Block
Receive
ATM
Cell Processor
Block
Receive
ATM
Cell Processor
Block
Transmit
PPP
Processor
Block
Transmit
PPP
Processor
Block
Receive
PPP
Processor
Block
Receive
PPP
Processor
Block
Receive
STS-3/12
TOH
Processor
Block
Receive
STS-3/12
TOH
Processor
Block
Transmit
STS-3/12
TOH
Processor
Block
Transmit
STS-3/12
TOH
Processor
Block
Receive
STS-3/12
POH
Processor
Block
Receive
STS-3/12
POH
Processor
Block
Transmit
STS-3/12
POH
Processor
Block
Transmit
STS-3/12
POH
Processor
Block
STS-3/12
Telecom
Bus
Interface
Block
STS-3/12
Telecom
Bus
Interface
Block
STS-3/12
PECL
Interface
Block
STS-3/12
PECL
Interface
Block
STS-3/12
CDR
Block
STS-3/12
CDR
Block
XRT95L34 – Channel 0
Transmit
POS-PHY
Interface
Block
Transmit
POS-PHY
Interface
Block
Receive
POS-PHY
Interface
Block
Receive
POS-PHY
Interface
Block
Clock
Synthesizer
Block
Clock
Synthesizer
Block
Microprocessor
Interface
Block
Microprocessor
Interface
Block
The operation of the “Receive STS-3c POH Processor” block is discussed in some detail below.
2.3.2.1
POINTER PROCESSING
As the XRT94L33 receives an incoming STS-3 data-stream, the Receive STS-3 TOH Processor block has the
responsibility
of
de-scrambling
this
incoming
data-stream,
and
acquiring
and
maintaining
frame
synchronization with the incoming STS-3 frames. Once these incoming STS-3 frames have been located; the
Receive STS-3c POH Processor block has the responsibility of locating and keeping track of the STS-3c
SPEs within this STS-3 data-stream.
As required by the SONET/SDH standards, the Receive STS-3c POH Processor blocks accomplish this by
monitoring the contents of each set of H1 and H2 bytes within the incoming STS-3 data-stream.
If a Given Channel is Receiving an STS-3c Signal
If a given channel is configured to receive an STS-3c signal, then each incoming STS-3 frame consists of a
single STS-3c SPE. The Receive STS-3c POH Processor block determines the location of this one STS-3c
SPE by the contents of the H1 and H2 byte the TOH of the incoming STS-3c data-stream.
The H1 and H2 Bytes within an STS-3c Signal