Altera Corporation
3–117
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Dynamic Reconfiguration
Based on your settings in these fields, the ALT2GXB MegaWizard
determines whether the
refclk
pre-divider should be enabled. For
example, if you select the
SONET/SDH OC-12
protocol in the
what is the
reconfig protocol driven by clock0
option, the ALT2GXB megafunction
automatically enables the
refclk
pre-divider and connects the output of
the pre-divider to the input reference clock port of the TX PLLs and
RX PLLs. Similarly, if you select the input clock frequency greater than
325 MHz, the
refclk
pre-divider is enabled.
When you select the
Use clock 0 reference clock divide
r option, the
Quartus II software instantiates the
refclk
pre-divider for the clock
input.
If the information provided in the
General
and
Reconfig Alt Pll
tabs
meet one of the conditions specified in
“Using Dedicated refclks” on
page 3–92
, the Quartus II software automatically instantiates the
refclk
pre-divider for the corresponding clock input. For other clock inputs, you
should determine whether the clock input frequency and the data rate
meets one of the conditions specified in
“Using Dedicated refclks” on
page 3–92
.
Example of a Condition to Select this Option:
Assume that you are using a clock input with a 125 MHz to configure the
TX PLL to run the channel at the 3.125 Gbps data rate. In this case, the
ratio of TX PLL data rate to input clock frequency is 25. This meets
condition 2 specified in
“Using Dedicated refclks” on page 3–92
.
Therefore, select this option so that the Quartus II software instantiates
the
refclk
pre-divider for this clock source.
1
When the Quartus II software creates a pre-divider for a
dedicated input reference clock (
refclk
), only the output of the
pre-divider is available to clock the TX PLL and /or RX PLL.
1
If you would like to reuse the MIF across transceiver channels,
you must have the same order of clock inputs across all the
ALT2GXB instantiations that are using this MIF.