EP4SE360F35I4 Datasheet, PDF (297/432 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
8–17
Differential Receiver
The Stratix IV device family has a dedicated circuitry to receive high-speed
differential signals in row I/Os. Figure 8–12 shows the hardware blocks of the
Stratix IV receiver. The receiver has a differential buffer and left and right PLLs that
can be shared between the transmitter and receiver, a DPA block, a synchronizer, a
data realignment block, and a deserializer. The differential buffer can receive LVDS,
mini-LVDS, and RSDS signal levels, which are statically set in the Quartus II software
Assignment Editor.
The left and right PLL receives the external clock input and generates different phases
of the same clock. The DPA block chooses one of the clocks from the left and right PLL
and aligns the incoming data on each channel. The synchronizer circuit is a 1 bit wide
by 6 bit deep FIFO buffer that compensates for any phase difference between the DPA
clock and the data realignment block. If necessary, the user-controlled data
realignment circuitry inserts a single bit of latency in the serial bit stream to align to
the word boundary. The deserializer includes shift registers and parallel load
registers, and sends a maximum of 10 bits to the internal logic.
The Stratix IV device family supports three different receiver modes:
■ “Non-DPA Mode” on page 8–22
■ “DPA Mode” on page 8–24
■ “Soft-CDR Mode” on page 8–25
The physical medium connecting the transmitter and receiver LVDS channels may
introduce skew between the serial data and the source-synchronous clock. The
instantaneous skew between each LVDS channel and the clock also varies with the
jitter on the data and clock signals as seen by the receiver. The three different modes—
non-DPA, DPA, and soft-CDR—provide different options to overcome skew between
the source synchronous clock (non-DPA, DPA) /reference clock (soft-CDR) and the
serial data.
1 Only non-DPA mode requires manual skew adjustment.
September 2012 Altera Corporation
Stratix IV Device Handbook
Volume 1