Re: [Discuss-gnuradio] FPGA/FX2 interface

[Eric Blossom]

On Thu, Jul 27, 2006 at 08:35:08PM -0700, Oussama Sekkat wrote:
> Hi
> I am looking at the usrp_std.v module and the schematics for the FPGA and
> the FX2/FPGA interface.
> It seems to me that the data of course arrives as a serial input to the 
> FX2
> chip. Then, it gets to the FPGA as a 16bit parallel input from the GPIF 
> bus.
> That input is called usb_data in the FPGA. However, upon reading the 
> verilog
> code of the serial_io.v module, it seems that this module does a serial to
> parallel conversion of the SDI input and puts it into the 32 bit 
> serial_data
> output register.  I am confused as to whether the serial data from the USB
> is converted to parallel  in the FX2 chip or whether the data sent to the
> FPGA  is serial but a verilog module inside the FPGA converts it to
> parallel. So I am not sure whether the data coming from the USB to the
> usrp_std.v module is the 16bit input usb_data or the SDI input.
> 
> Thank you ahed of time,
> Oussama.

serial_io.v is only used for writing and reading the FPGA registers.
The actual data to/from the DACs/ADCs (DUCs/DDCs) goes across the
16-bit GPIF bus. 

Eric