PLLs & Clock Networks
Figure 2–39. External PLL Output Clock Control Blocks
PLL Counter
Outputs (c[5..0])
6
Static Clock Select
(1)
Enable/
Disable
Internal
Logic
IOE (2)
Internal
Logic
Static Clock
Select
(1)
PLL_OUT
Pin
Notes to Figure 2–39:
(1) These clock select signals can only be set through a configuration file (.sof or .pof)
and cannot be dynamically controlled during user mode operation.
(2) The clock control block feeds to a multiplexer within the PLL_OUTpin’s IOE. The
PLL_OUTpin is a dual-purpose pin. Therefore, this multiplexer selects either an
internal signal or the output of the clock control block.
For the global clock control block, the clock source selection can be
controlled either statically or dynamically. The user has the option of
statically selecting the clock source by using the Quartus II software to set
specific configuration bits in the configuration file (.sof or .pof) or the
user can control the selection dynamically by using internal logic to drive
the multiplexor select inputs. When selecting statically, the clock source
can be set to any of the inputs to the select multiplexor. When selecting
the clock source dynamically, you can either select between two PLL
outputs (such as the C0 or C1 outputs from one PLL), between two PLLs
(such as the C0/C1 clock output of one PLL or the C0/C1 c1ock output of
the other PLL), between two clock pins (such as CLK0or CLK1), or
between a combination of clock pins or PLL outputs. The clock outputs
from corner PLLs cannot be dynamically selected through the global
control block.
For the regional and PLL_OUTclock control block, the clock source
selection can only be controlled statically using configuration bits. Any of
the inputs to the clock select multiplexor can be set as the clock source.
2–56
Stratix II Device Handbook, Volume 1
Altera Corporation
May 2007
ALTERA [ ALTERA CORPORATION ]
