hi dave,
the lvds pairs are programmable - you can use
any pair for transmitting, or receiving, and you
can select if you want termination.
dan
On 01/25/2010 10:24 AM, David Hawkins wrote:
Hi Dan,
there's a samtec connector on the roach with 40 LVDS pairs.
you can buy a cable from samtec that connects two roaches together
using this connector. (i think it's a samtec "QSH" connector).
there's also a ZDOC to VSI connector board developed by
haystack observatory for VLBI. you can plug these boards into
roaches and then connect them together with a VSI cable.
Just a caveat, that I'm not sure applies here ...
Can the ROACH LVDS signals be defined as RX or TX?
Most LVDS SERDES in FPGAs are unidirectional, so
if you want a transceiver, you need to wire pairs
of LVDS signals (4 pins) during the PCB layout.
I don't recall if this was done on the ROACH board
at the Z-DOK connectors.
If the LVDS signals are not wired this way, you
could still wire two ROACH boards together, but you'd
have to use 3.3V (or 2.5V) single-ended signals.
Cheers,
Dave
--
Dan Werthimer
Space Sciences Lab and Berkeley Wireless Research Center
University of Calfornia, Berkeley
