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XRM(2)-DAC-D4/1G User Guide
V2.2 - Mar 8, 2018
Figure 7 : Kintex 7 Virtex 7 Clocking Scheme
The remaining clock inputs are used for clock monitoring and diagnostic purposes only
2.13 Data Generation
Each DAC receives data via a 16-bit DDR interface, plus DCLK, generated by the data source synchronously
with the data. Clock speed restrictions in the FPGA force the use of OSERDES components in order to be able
to run at the full rate (1G sample per second) This in turn means that the data generation circuitry must provide
4 consecutive data samples on each FABRCLK clock cycle.
In the example code this is implemented by instantiating four identical data sources for each type of waveform
produced, each offset by the appropriate amount in order to provide the correct signal for each time slot.
2.14 Performance
Typical performance when producing a 125 MHz sine wave using the internal 1GHz clock is shown below. Note
that the figure shows both the fundamental frequency (F
fund
) and the image frequency (F
sample
-F
fund
) of the
fundamental caused by sampling. The image frequency and higher components are normally filtered out by a
low-pass filter which has a cut-off frequency F
cutoff
<= F
sample
/2, the midpoint of the figure.
Page 15
Hardware
xrm-dac-d4-1g-manual_v2_2.pdf