hi richard,
while many casperites have built synchronous instruments,
in general, for large systems with multiple boards,
i recommend an asynchronous design (each processing board
running on it's own clock), like the casper packetized
correlator/beamformer or like a computer cluster.
i usually recommend synchronous systems for a small
number of boards (two to four boards), and there are good
ways to keep the data in sync as it moves from board to
board over xaui (eg: see the responses to your email query).
a packetized async system adds some complexity to transmit
and receive packets, but provides a flexible,
scalable, fault tolerent, upgradeable system -
you can add linux computers, GPU's, specialized
low power ASIC processors, software beamformers and correlators,
switches, bee3's, roach II's, cray's,
all connected together with industry standard 10Gbe protocol.
best wishes,
dan
On 08/28/2009 07:52 AM, Richard Armstrong wrote:
Hi Jason,
Apologies for confusion, I'm using the scheme as you described: a
counter lsb driving the IBOB SMA. This 1/2 speed output clock is
level-converted and runs to the BEE2 user clock SMA input. BEE2 designs
run off usr_clk2x. I don't know of any way to connect the ibob clock
signal directly.
Thanks again, and I look forward to your reply.
I'm doing some more testing this afternoon and will see if I can get
Billy's scheme up and running.
Peace,
~R
2009/8/28 Jason Ray <[email protected] <mailto:[email protected]>>
On Fri, 28 Aug 2009, Richard Armstrong wrote:
This week I've been trying to clock the BEE2 off an
IBOB-generated clock
with an LVTTL-to-LVPECL clock driver. I changed the BEE2 design
and changed
a jumper to select user-clock on the BEE2 board. Unfortunately,
this doesn't
seem to help much (although, I could be doing it wrong) and I'm
finding with
this scheme that the BEE2 has the tendancy to kill the running
process after
a few seconds to minutes.
Admittedly, I have not fully read though all of the replies on this
thread yet, so this might have already been covered....
But, if you want the BEE2 running at the same clock rate as your
iBOB's, I think you'll need to select usr_clk2x on the BEE2 and in
the BEE2 model file. Unless there's some other way that Randy & I
couldn't find, the best you can do is connect the LSB of a counter
to the iBOB SMA output. This gives you 1/2 the clk rate of the
iBOB. So, you'd be driving the BEE2 at 1/2 the rate, unless you use
usr_clk2x which multiplies the incoming clock by two to get you back
to the same rate.
Is there some way to connect the actual iBOB clock signal to the SMA
GPIO in the model file?
Jason
--
Richard Armstrong
ʞn˙ɔɐ˙xo˙oɹʇ...@ƃuoɹʇsɯɹɐ˙pɹɐɥɔıɹ
+44 (0) 79 0682 9979 (UK mobile)
+44 (0) 1865 273597 (Office)
--
Dan Werthimer
Space Sciences Lab and Berkeley Wireless Research Center
University of Calfornia, Berkeley
