Xilinx VCU128 User Manual

Programmable QSFP2 Clock
[Figure 2, callout 14]
The VCU128 evaluaon board has a SI570 I2C programmable low-jier 3.3V LVDS dierenal
oscillator (U90) connected to FPGA U1 GTY bank 134 MGTREFCLK0 P/N pins T42 and T43
(series capacitor coupled), respecvely.
On power-up, the U90 SI570 user clock defaults to an output frequency of 156.250 MHz. The
Zynq-7000 SoC system controller or FPGA implemented user IP can change the output
frequency within the range of 10 MHz to 810 MHz through an I2C interface. Power cycling the
VCU128 evaluaon board resets the QSFP2 clock to the default frequency of 156.250 MHz.
• Programmable oscillator: Silicon Labs Si570BAB0000544DG (10 MHz-810 MHz)
• Frequency tolerance: 50 ppm
• 3.3V LVDS dierenal output
The programmable QSFP2 clock circuit is shown in the following gure.
Figure 14: QSFP2 Clock
X21964-121918
Chapter 3: Board Component Descriptions
UG1302 (v1.0) December 21, 2018 www.xilinx.com
VCU128 Board User Guide 44
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Xilinx VCU128 Specifications

General

Brand	Xilinx
Model	VCU128
Category	Motherboard
Language	English