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Re: [Discuss-gnuradio] Purpose of extra two bits sent to FX2 chip with d
Re: [Discuss-gnuradio] Purpose of extra two bits sent to FX2 chip with data samples
Sat, 31 Jan 2009 21:57:31 -0800
On Sun, Feb 01, 2009 at 12:30:58AM -0500, Paul Creekmore wrote:
> The FPGA on USRP1 sends an extra two bits of data with each 16-bit word
> (to the FX2 chip). If I'm not mistaken, the first bit is set when
> accompanying a sample from rx channel 0, and the second bit is set when
> accompanying an inphase (as opposed to quadrature) sample (presumably
> from channels 0, 2, 4, or 6).
> * What significance do these two bits have in the handling of the data
> after the FPGA?
> I'm trying to figure out how best to set these bits in the case of
> packed samples at lower quantization levels.
Uhh, what two extra bits? The GPIF bus is 16-bits wide...
The FPGA does report two status bits (independent of the data bits)
that indicate whether (1) it has room for a new packet from the FX2
and (2) if it has a packet available for the FX2. I don't think
anything you're doing should have anything to do with how those flags
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