2–120
Altera Corporation
Stratix II GX Device Handbook, Volume 2
October 2007
PLD-Transceiver Interface Clocking
The
rx_cruclk
and the
pll_inclk
are reference clocks to the
transceiver receiver PLL and transmitter PLL. These two ports can take
the reference clock from the dedicated
REFCLK
pins or from the PLD
global clock pins. If the PLD global clock pins are used to feed the
transceiver PLLs, a PLD interface clock will be used for each independent
reference clock feeding the transceiver.
Each transceiver block has one possible PLD connection to
pll_inclk
and four possible connections to
rx_cruclk
. Only one reference clock
frequency can be fed from the PLD to each transceiver block. The receiver
PLLs of each channel can possibly have a different reference clock
frequency as long as there are PLD interface clocks available.
The
tx_coreclk
and
rx_coreclk
are input clocks to the transmitter
and receiver phase compensation FIFOs, respectively. By default, the
Quartus II software automatically routes the
tx_clkout
or
coreclk_out
to the
tx_coreclk
, and the
rx_clkout
,
tx_clkout
, or
coreclk_out
to the
rx_coreclk
port, depending on the transceiver
block and channel configuration as listed in the above section.
There are options to route other PLD clocks to the
tx_coreclk
and
rx_coreclk
ports. The non-transceiver clocks that feed these ports are
required to be frequency locked (0 ppm) to the transceiver output clocks
of the associated channel or transceiver block, depending on the
configuration. The method of using this option is discussed in a later
section.
The
cal_blk_clk
feeds the calibration block.
If a single clock from the PLD feeds multiple ports listed above, then only
one PLD interface clock will be used. It is recommended that whenever
possible, utilize a common clock. This will save PLD clock resources and
PLD interface resources.
Each transceiver block (with all channels running in the same
configuration), by default, uses a minimum of five PLD interface clocks
as seen in
Figure 2–98
. This is with each
rx_coreclk
clocked by the
associated
rx_clkout
of each RX channel, and since all the TX channels
are the same, the Quartus II software will automatically route
tx_clkout[0]
to all the
tx_coreclk
inputs. The reference clock can
use the dedicated
REFCLK
pins to save on PLD interface clocks. The
Quartus II software does not cross the transceiver block boundary when
combining like TX channels. Also, the Quartus II software does not
combine RX clocks automatically.
Содержание Stratix II GX
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