EP4SE360F35I4 Datasheet, PDF (305/432 Pages) Altera Corporation – This section provides a complete overview of all features relating to the Stratix IV device family, which is the most architecturlly advanced

Chapter 8: High-Speed Differential I/O Interfaces and DPA in Stratix IV Devices
Differential Receiver
8–25
Soft-CDR Mode
The Stratix IV LVDS channel offers soft-CDR mode to support the Gigabit Ethernet
and SGMII protocols. A receiver PLL uses the local clock source for reference.
Figure 8–20 shows the soft-CDR mode datapath.
Figure 8–20. Receiver Datapath in Soft-CDR Mode ⁽¹⁾, ⁽²⁾, ⁽³⁾
10
rx_out
IOE Supports SDR, DDR, or Non-Registered Datapath
2
IOE
FPGA
Fabric
rx_divfwdclk
rx_outclock
Deserializer
DOUT DIN
Bit Slip
DOUT DIN
2
(LOAD_EN, diffioclk)
diffioclk
Clock Mux
LVDS Receiver
+
rx_in
Synchronizer
DOUT DIN
DPA Circuitry
Retimed
Data
DIN
DPA Clock
3
(DPA_LOAD_EN,
DPA_diffioclk,
rx_divfwdclk)
3 _{(LVDS_LOAD_EN,}
LVDS_diffioclk,
rx_outclk)
Left/Right PLL
rx_inclock
Notes to Figure 8–20:
(1) All disabled blocks and signals are grayed out.
(2) In SDR and DDR modes, the data width from the IOE is 1 and 2 bits, respectively.
(3) The rx_out port has a maximum data width of 10 bits.
8 Serial LVDS
Clock Phases
LVDS Clock Domain
DPA Clock Domain
In soft-CDR mode, the synchronizer block is inactive. The DPA circuitry selects an
optimal DPA clock phase to sample the data. Use the selected DPA clock for bit-slip
operation and deserialization. The DPA block also forwards the selected DPA clock,
divided by the deserialization factor called rx_divfwdclk, to the FPGA fabric, along
with the deserialized data. This clock signal is put on the periphery clock (PCLK)
network. When using soft-CDR mode, the rx_reset port must not be asserted after
the DPA training is asserted because the DPA will continuously choose new phase
taps from the PLL to track parts per million (PPM) differences between the reference
clock and incoming data.
f For more information about periphery clock networks, refer to the Clock Networks and
PLLs in Stratix IV Devices chapter.
September 2012 Altera Corporation
Stratix IV Device Handbook
Volume 1