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Re: [Discuss-gnuradio] Alternative interface from PC to a USRP.

From: Lamar Owen
Subject: Re: [Discuss-gnuradio] Alternative interface from PC to a USRP.
Date: Sat, 9 Jul 2005 14:36:27 -0400
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On Saturday 09 July 2005 12:58, David Carr wrote:
> How many pins does Ultra320 require, is it 32x2 (differential) = 64?

The connector is a 68 pin connector, and the bus is 16 bits.  By using two 68 
pin connectors you can get 32 bits wide; very few host adapters are available 
to do that, but that would get you 640MB/s (160megawords per second).

> Also what are the max cabling lengths at this speed?

For LVD Ultra 320 SCSI, the max bus length (terminator to terminator) cannot 
exceed 12 meters (39 feet).

For single-ended (non-twisted pair cable) the max length varies according to 
speed.  For 40MB/s (20 megatransfers per second) SE can go 1.5 meters; for 
20MB/s 3 meters, and for 10 MB/s (5 MT/s) 6 meters.

> What is the clock rate on those pins?

160MHz, low voltage differential on twisted pair.

> You mention the ability to send data between hosts without CPU
> intervention.  Does that mean its possible to send data from the USRP to
> multiple hosts connected on the same SCSI bus?


> By the way I think that gigabit is 1Gbps full-duplex ie: 2Gbps.

Sure, if you are doing both transmit and receive.  But you would be limited to 
1Gb/s for receive-only. 
Lamar Owen
Director of Information Technology
Pisgah Astronomical Research Institute
1 PARI Drive
Rosman, NC  28772

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