DE5-Net User Manual
June 20, 2018
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The development board includes one 50 MHz and three programmable oscillators
shows the default frequencies of on-board all external clocks going to the Stratix V GX FPGA. The
figures also show an off-board external clock from PCI Express Host to the FPGA.
Figure 2-9 Clock circuit of the FPGA Board
A clock buffer is used to duplicate the 50 MHz oscillator, so each bank of FPGA I/O bank 3/4/7/8
has two clock inputs. The three programming oscillators are low-jitter oscillators which are used to
provide special and high quality clock signals for high-speed transceivers.
control circuits of programmable oscillators. The clock generator controller in the MAX II CPLD
can be used to program the CDCM61001 and CDCM61004 to generate 1G Ethernet SFP+ and
SATA reference clocks respectively. The Si570 programmable clock generator is programmed via
an I2C serial interface to generate the 10G Ethernet SFP+ reference clock. Two SMA connectors
provide external clock input and clock output respectively.