Forum: FPGA, VHDL & Verilog PCIe Hard IP ("Hardcore") and Tandem Moethod Confuse..

von Paul Y. (ysm)

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People say there's a PCIe Endpoint "Hard Core" inside the Virtex 7 FPGA.
But, from what I see in some documents, there's Hard IP in a flash 
outside of the FPGA, which is load via a CPLD to the FPGA. Xilinx calls 
this Tandem Method, Altera calls it CvP.

And if the ASIC in side the FPGA exits in Virtex 7, why do we need the 
Tandem Method?

von Achim S. (Guest)

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The "hardware" for PCIe is present in the FPGA, but nevertheless it 
needs to be configured after startup to run properly (like pretty much 
everything in the FPGA). This configuration data is read from the 
external Flash.

The configuration takes some time, and that delay might be too long in a 
PCIe system. It might happen, that due to the configuration-delay the 
PCIe device gets not properly recognized in the system.

The special thing about the "tandem method" is, that first a small part 
of the configuration is loaded quite fast (so that the PCIe device is 
functional in time). The long lasting configuration of the complete FPGA 
is then done in a second step (either from Flash, or over the 

von Paul Y. (ysm)

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Thank you.
So I guess Xilinx calls the 'hardware' the 'Integrated Block', and the 
integrated block IS an ASIC inside FPGA.
Again, thanks.


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