QT2022/32 - Data Sheet: DS3051
5 Datapath Description
This section describes the functional blocks of the QT2022/32. These are illustrated in Figure 2.
Figure 2: QT2022/32 Functional Block Diagram
EREFCLK
clock
TXPLLOUT
SREFCLK
(QT2032 only)
generator
VXCOI
TxXAUI0
TxXAUI1
TxXAUI2
TxXAUI3
Code
Sync
CDR
CDR
CDR
CDR
Code
Sync
Phase
Adjust &
Demux
Scrambler
Output
Driver
64b/66b
Encoder
WIS
TX
(QT2032
only)
TXOUT
Rate
10b/8b
Align
Gearbox
Mux
Adjust
Decoder
Code
Sync
Code
Sync
WIS
AMCC
AMCC
PMA
3.125 Gb/s
RxXAUI0
XGXS
network
loopback
PMA
loopback
XGXS
PCS
system
loopback
loopback
network
loopback
system
loopback
(QT2032 only)
DRV
DRV
DRV
DRV
RxXAUI1
RxXAUI2
RxXAUI3
8b/10b
Frame
Sync
RXIN
WIS
RX
(QT2032
De-
scrambler
66b/64b
Decoder
Rate
Demux
CDR
Adjust
Encoder
only)
limiting
amp
freq
mon
LOS
detector
RXPLLOUT
EEPROM_SDA
EEPROM_SCL
MDIO
MDC
MDIO Control
Interface
EEPROM / DOM
Interface
sync_err
LOSOUTB
EEPROM_PROT
5.1 Transmit Path
5.1.1 XAUI CDR and Demultiplexer
At the transmitter XAUI interface, clock and data are recovered for each of the four 3.125Gb/s input lanes. The dif-
ferential receivers used at this interface have 100Ω differential input impedance and are intended to be AC coupled
or 1.2V CML DC coupled. The data on each channel is then demultiplexed/deserialized before being passed to the
next block. A clock is recovered for each lane. Each lane outputs a status bit, xtxlock<3:0>, which is high when the
CDR circuit is in lock. A phase-adjust FIFO aligns the four lanes using the Lane 1 recovered clock.
5.1.2 XAUI Code Synchronization
The XAUI interface demultiplexer has no prior knowledge of code word boundaries and must determine where
each 8B/10B character starts and ends. To achieve this, the code synchronization block searches the data stream
for the unique comma character, /K/, in order to determine the 10 bit code word boundaries for each lane. The
delimited code words are passed to the Frame Deskew block. The code synchronization status is displayed in Reg-
ister bits 4.18h.3:0.
The comma characters, /K/, are found in the XAUI data stream in the IPG between packets.
Revision 5.11
AppliedMicro - Confidential & Proprietary
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AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
