2–204
Altera Corporation
Stratix II GX Device Handbook, Volume 2
October 2007
Native Modes
1
The maximum number of CPRI channels per device also
depends on the number of transceiver channels available in that
device and the LRIO clock resource limitations.
CPRI mode is supported only in C3, C4, and I4 speed-grade devices.
PLD-Transceiver Interface Clock Duty Cycle
Due to delay adjustments made to the
tx_clkout
and
rx_clkout
routes in the FPGA clock network, the worst case duty cycle on these
PLD-transceiver interface clocks can be 60-40%. If these clocks are used to
clock FPGA logic array, you must set proper timing analyzer assignments
to account for the 60-40% duty cycle on these clocks.
Figure 2–150
shows how to set 60-40% duty cycle constraints in
TimeQuest Timing Analyzer for a CPRI 614.4 Mbps line rate
configuration. In the TimeQuest Analyzer window, selecting the
Report
Clocks
option lists all the
tx_clkout
and
rx_clkout
clocks in your
design. Select all clocks and adjust the falling edge timing appropriately
for 60-40% duty cycle.
Figure 2–150. Setting Duty Cycle in TimeQuest Timing Analyzer
Figure 2–151
shows how to set 60-40% duty cycle constraints in Classic
Timing Analyzer. To set this option, go to the Assignments menu and
select
Settings
, then select
Timing Analysis Settings
and
Classic Timing
Analyzer Settings
, and then click on the
Individual Clocks
tab. In the
Individual Clocks
window, select
New
. In the
New Clock Settings
window, browse to all
rx_clkout
and
tx_clkout
nodes and assign
60%
in the
Duty Cycle
option for each of these phase compensation FIFO
clocks.