Electronics > FPGA
NCO to generate square wave
hamster_nz:
> Do any of the regular pins on spartan 7 work in that 1Gbps mode?
Yes. Different grades have different speeds.
See table 15 (on page 15) of https://www.xilinx.com/support/documentation/data_sheets/ds181_Artix_7_Data_Sheet.pdf for specs.
BrianHG:
Dont know about spartan, but with altera, I do know that you can get the DDR DQ pins to do the 1GHz unbalanced, IE 2.5v or 3.3v outputs. Meaning a 1ns jitter with with a NCO. (Note that I have 2 projects online here at EEVblog which do run CycloneIV and Max10 at this 1GHz with read/write data, so I know it can be done. I got the bottom end slowest CycloneIV to transmit HDMI at 1.08GHz through regular DDR-DQ pins.)
It is probably the same with Spartan unless you use LVDS dedicated transmitters which are balanced low voltage outputs. LVDS usually means 1.8 or 1.5v output, but 2 of them per channel which will need a differential receiver to amplify each channel. Spartan 7 is a faster FPGA than CycloneIV/MAX10. I would only choose MAX10 if you want low power and no bootprom as 16 NCOs running at 100MHz driving a 10:1 serdes transmitter would only draw something like 50-100ma VCC on a Cyclone/Max10. Though, the MAX10 will require a compiler workaround to run it's outputs at 1GHz.
langwadt:
--- Quote from: Evan.Cornell on December 08, 2021, 10:58:48 pm ---Do any of the regular pins on spartan 7 work in that 1Gbps mode?
--- End quote ---
afair SERDES and DDR is available on all pins (~1Gbps need LVDS so pair of pins)
hamster_nz:
--- Quote from: langwadt on December 08, 2021, 11:57:59 pm ---
--- Quote from: Evan.Cornell on December 08, 2021, 10:58:48 pm ---Do any of the regular pins on spartan 7 work in that 1Gbps mode?
--- End quote ---
afair SERDES and DDR is available on all pins (~1Gbps need LVDS so pair of pins)
--- End quote ---
But when you are generating a square wave at about 1MHz +/-50kHz then a single-ended output buffer will be just fine.
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