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Transceiver Clocking and Channel Placement Guidelines in XAUI Configuration
Transceiver Clocking
Figure 4-21: Transceiver Clocking for XAUI Configuration
One of the two channel PLLs configured as a CMU PLL in a transceiver bank generates the transmitter serial
and parallel clocks for the four XAUI channels. The x6 clock line carries the transmitter clocks to the PMA
and PCS of each of the four channels.
RX
Phase
Compensation
FIFO
TX
Phase
Compensation
FIFO
Byte
Serializer
Receiver Standard PCS
Receiver PMA
Deserializer
CDR
Transmitter Standard PCS
Transmitter Standard PCS
Transmitter Standard PCS
Transmitter Standard PCS
Channel 0
Channel 1
Channel 2
Channel 3
Transmitter PMA Ch 0
Transmitter PMA Ch 1
Transmitter PMA Ch 2
Transmitter PMA Ch 3
Serializer
tx_serial_data
rx_serial_data
Parallel Clock
Parallel Clock (Recovered)
Byte
Deserializer
8B/10B
Decoder
Rate
Match
FIFO
Deskew
FIFO
Word
Aligner
8B/10B
Encoder
Soft PCS
Soft PCS
Soft PCS
Soft PCS
FPGA Fabric
Channel 3
Channel 2
Channel 1
Channel 0
16
16
20
20
20
20
10
10
xgmii_tx_clk
xgmii_rx_clk
/2
Parallel Clock
(Recovered) from Channel 0
Parallel Clock
/2
Clock Divider
Parallel and Serial Clocks (From the ×6 or ×N Clock Lines)
Serial Clock
(From the ×1 Clock Lines)
Central/ Local Clock Divider
Parallel Clock
Serial Clock
Parallel and Serial Clocks
CMU PLL
Table 4-7: Input Reference Clock Frequency and Interface Speed Specifications for XAUI Configurations
FPGA Fabric-Transceiver Interface
Frequency (MHz)
FPGA Fabric-Transceiver Interface Width
Input Reference Clock Frequency
(MHz)
156.25
16-bit data, 2-bit control
156.25
Transceiver Clocking Guidelines for Soft PCS Implementation
In the soft PCS implementation in the XAUI configuration, you must route
xgmii_rx_clk
to
xgmii_tx_clk
as shown in the following figure.
This method uses
xgmii_rx_clk
to compensate for the phase difference on the TX side.
Without this method, the
tx_digitalreset
signal may experience intermittent failure.
Transceiver Protocol Configurations in Cyclone V Devices
Altera Corporation
CV-53004
Transceiver Clocking and Channel Placement Guidelines in XAUI Configuration
4-22
2013.10.17