AXI Bridge for PCI Express v2.4
45
PG055 June 4, 2014
Chapter 3:
Designing with the Core
The MMCM generates the following clocks for PCIe solution wrapper:
• clk_125mhz - 125 MHz clock.
• clk_250mhz - 250 MHz clock.
• userclk - 62.5 MHz / 125 MHz / 250 MHz clock, depending on selected PCIe core lane
width, link speed, and AXI interface width.
• userclk2 – 250 MHz / 500 MHz clock, depending on selected PCIe core link speed.
• oobclk – 50 MHz clock.
The other cores/logic present in the user design can use any of the MMCM outputs listed
above.
The MMCM instantiated in the PCIe example design has two unconnected outputs:
clkout5
, and
clkout6
. You can use those outputs to generate other desired clock
frequencies by selecting the appropriate CLKOUT5_DIVIDE and CLKOUT6_DIVIDE
parameters for MMCM.
X-Ref Target - Figure 3-3
Figure 3-3:
Shared Clocking