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Chapter 8: Reset and Clocks
8–7
Clocks
June 2012
Altera Corporation
Stratix V Hard IP for PCI Express
pld_clk
coreclkout_hip
can drive the Application Layer clock along with the
pld_clk
input
to the Stratix V Hard IP for PCI Express IP Core. The
pld_clk
can optionally be
sourced by a different clock than coreclkout_hip. The
pld_clk
minimum frequency
cannot be lower than the
coreclkout_hip
frequency. Based on specific Application
Layer constraints, a PLL can be used to derive the desired frequency.
Additional Clocks
Designs that include the Stratix V Hard IP for PCI Express may require the following
additional clocks:
hip_reconfig_clk
The frequency range for this clock is 50–125 MHz. This is the clock signal for the Hard
IP reconfiguration interface. You can use this interface to change the value of global
configuration registers that are read-only at run time. Use of the reconfiguration
interface is optional.
reconfig_xcvr_clk
This is a free running clock with a frequency range of 100–125 MHz. This is the clock
input to the Transceiver Reconfiguration Controller which performs the transceiver
PHY reconfiguration functions required by Gen2 and Gen3 designs. For more
information, refer to
“Transceiver PHY IP Reconfiguration” on page 14–9
.
Clock Summary
summarizes the clocks for designs that include the Stratix V Hard IP for PCI
Express IP Core.
×8
Gen3
256
250 MHz
:
(1) The 256-bit interface is only available for the Avalon-ST interface.
(2) This mode saves power.
Table 8–2. coreclkout_hip Values for All Parameterizations
Link Width
Max Link Rate
Avalon Interface Width
(1)
coreclkout_hip
Table 8–3. Required Clocks (Part 1 of 2)
Name
Frequency
Clock Domain
Clock Used by the Stratix V Hard IP for PCI Express IP Core
coreclkout_hip
125, or 250 MHz
Avalon-ST interface between the Transaction and Application
Layers.
pld_clk
62.5, 125 MHz, or 250 MHz
Application and Transaction Layers.
refclk
100 or 125 MHz
SERDES (transceiver). Dedicated free running input clock to
the SERDES block.
Other Clocks that May Be Required for PCI Express Designs