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13 years ago

[Timequest] SDR edge aligned constraints support

I read some documentation about the source synchronous interface (Rysc one, AN433, altera web site etc...) but it's still a bit confusing for me.

So, my Stratix V is interfaced with a ADC AD9230 wich provides SDR edge aligned 12 bits parallel data '"adc_d_ext" and a 200 MHz clock signal "adc_dco_ext".

The ADC datasheet indicates a skew between the data and clock of -0.3 ns min and +0.5 ns max.

I followed litterature recommendations so I use a fPLL in source synchronous mode sourced by adc_dco_ext to generate a 180° shifted clock to latch the data bus inside the FPGA.

The sdc constraints are :

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derive_pll_clocks -create_base_clocks

derive_clock_uncertainty

create_clock -period 5 -name adc_dco_ext [get_ports {adc_dco_ext}] -- creation of the FPGA input clock (source of the PLL)

create_clock -period 5 -name virt_adc_dco_ext -- creation of the ADC virtual clock

set_input_delay -add_delay -clock virt_adc_dco_ext -max 0.5 [get_ports {adc_d_ext[*]}]

set_input_delay -add_delay -clock virt_adc_dco_ext -min -0.3 [get_ports {adc_d_ext[*]}]

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Do you think they are correct ?

Thank you very much for your support.