Altera Corporation
2–165
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
Figure 2–119
shows the timing diagram for the signals generated by the
NFRI_PLD_logic.
Figure 2–119. Timing for the Signals Generated by the NFRI_PLD_logic
Low-Latency PIPE mode
The Stratix II GX receiver data path employs a rate match FIFO in PIPE
mode to compensate up to ± 300 PPM difference between the upstream
transmitter and the local receiver reference clock. The rate match FIFO
adds a latency of 12-16 parallel clock cycles to the link. The low-latency
PIPE mode allows bypassing the rate match FIFO in synchronous systems
that derive the transmitter and receiver reference clocks from the same
source. You can bypass the rate match FIFO by not selecting the
Enable
Rate match FIFO
option in the ALT2GXB MegaWizard Plug-In Manager.
You can bypass the rate match FIFO in single-lane (×1), four-lane (×4) and
eight-lane (×8) PIPE modes. In normal PIPE mode, the receiver blocks
following the rate match FIFO are clocked by
tx_clkout
(×1 mode) or
coreclkout
(×4 and ×8 modes) of the local port. In low-latency mode,
since the rate match FIFO is bypassed, these receiver blocks are clocked
by the recovered clocks of the respective channels. As a result, the
channels in a multi-lane (×4 or ×8) low-latency PIPE mode are unbonded.
Except for the rate match FIFO being bypassed and the resulting changes
in transceiver internal clocking, the low-latency PIPE shares the same
data path and state machines as the normal PIPE mode. However, some
features supported in normal PIPE mode are not supported in
low-latency PIPE mode.
rx_dataout
pipedatavalid
pipeelecidle
rx_signaldetect
pipeelecidle_PLD
pipedatavalid_PLD
EIOS
FTS
forward the
pipeelecidle from the
ALT2GXB to the
user logic
forward the
pipedatavalid from
the ALT2GXB to the
user logic
3.2us
4us
Содержание Stratix II GX
Страница 640: ...4 244 Altera Corporation Stratix II GX Device Handbook Volume 2 October 2007 Document Revision History ...
Страница 642: ...4 246 Altera Corporation Stratix II GX Device Handbook Volume 2 October 2007 Document Revision History ...
Страница 672: ...6 14 Altera Corporation Stratix II GX Device Handbook Volume 2 October 2007 Document Revision History ...