3–92
Altera Corporation
Stratix II GX Device Handbook, Volume 2
October 2007
Channel and Clock Multiplier Unit (CMU) PLL Reconfiguration
f
For more information on LRIO resource limitation, refer to the PLD
Clock Resource section in the
Stratix II GX Transceiver Architecture
Overview
chapter in volume 2 of the
Stratix II GX Device Handbook
.
Using Dedicated refclks
When you use dedicated
refclks
as input reference clocks, the
refclk
pre-divider is required if
one
of the following conditions is satisfied:
1.
If the input clock frequency is greater than 325 MHz.
2.
For functional modes with a data rate less than 3.125 Gbps (the data
rate is specified in the
what is the data rate?
option in the
General
tab of the ALT2GXB MegaWizard). The TXPLL and RXPLL is
configured with the data rate that you set in this option.
●
If the input clock frequency is greater than or equal to 100 MHz
AND
●
If the ratio of data rate to input clock frequency is 4, 5, or 25
3.
For functional modes with an data rate greater than 3.125 Gbps:
●
If the input clock frequency is greater than or equal to 100 MHz
AND
●
If the ratio of data rate to input clock frequency is 8, 10, or 25
When you use the channel and CMU PLL reconfiguration feature, you
can dynamically reconfigure the TX PLLs and the RX PLL in a transceiver
block from any of the five available input reference clocks. The Quartus II
software automatically instantiates the
refclk
pre-divider (if one of the
above mentioned conditions is satisfied) for the clock sources that drive
the main and alternate TX PLL.
1
You specify the information for main and alternate TX PLL in
the
General
and
Reconfig Alt PLL
tabs, respectively.
For the other clock inputs, the ALT2GXB MegaWizard provides optional
options in the
Reconfig Clks 1
and
Reconfig Clks 2
tabs to specify
whether a
refclk
pre-divider should be instantiated by the Quartus II
software. The available options are:
a.
what is the reconfig protocol driven by clock x?
(“x” can be 0, 1, 2, 3, 4)
b.
what is clock x input frequency?
c.
use clock x reference clock divider?