[Cryptech Core] Fwd: FPGA issues (Was: Re: Current sync problem)

[Joachim Strömbergson]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

Aloha!

Randy Bush wrote:
> on the last call basil said something akin to a synchronous buffer,
> no clock, just signal buffer empty, wait for other side to say buffer
> is now full.  stupid enough even i could fool myself that i
> understood what he was saying.

Not sure I understand. You would need at least one clock in any
construct that handles clock domain boundary crossing. a fully
asynchronous block will not be able to hold any info and will also be
hard to get stable. Its behaviour will vary with placement on the FPGA
structure.

But it also sounds a bit like what I ment with a fifo where you have
syn- and ack-signals on both ends. The depth of the fifo can be as
little as one, but not less than that. In our case the fifo fed from the
clk133 domain would have at least storage for two elements to allow the
handling of double data rate.

You want to have ack-signals to allow inserting and extracting entities
connected to the fifo to know that their requests has been acknowledged.

If that is close to what Basil and you are thinking about then yes it
should potentially solve the boundary crossing issues. But the timing on
the EIM bus needs to be solved. And cleaning up the clock implementation
will quite probably also be needed.

- -- 
Med vänlig hälsning, Yours

Joachim Strömbergson - Alltid i harmonisk svängning.
========================================================================
 Joachim Strömbergson          Secworks AB          joachim at secworks.se
========================================================================
-----BEGIN PGP SIGNATURE-----
Version: GnuPG/MacGPG2 v2
Comment: GPGTools - http://gpgtools.org
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iQIcBAEBCAAGBQJUl9pXAAoJEF3cfFQkIuyNtpcQAKF1Tc/2EGKH+Glg7qTrG+et
yXZYcXZx6kFO5C0FEqoq3Tlq48z4rYv8UgJI3b9y1nfrAeO8qLbP+gDnUV8jMatv
QU5mVI5532XCe+dvnbg3B2dDC5spAUBQFlHZ5Jox1pHHXPPzBMTmhYXt+44yqfl7
xrxQtV//S10PmZ/ggplt4Jdxg5DAr/sChfmXDKidjSYFzW0pct5GRe/tPyZw5tBH
f6hHc5hvePhTaOSeQuDi7lqzxexmtOFRtkR3HVy4WNsaPrB6B34Go3oHMJsr1fmS
tzPrRVd9MoxrpaAIh8Sa5SMmPmax4pMWNfZiE4mKeWy/AMX3uRp05rVk4c13zly2
IjsiBMEoINTd/kOyKycB2a74xo+rneFhXpQkU3Ich+17d230QY3BATejIspr/ZXk
u3HkYAv87tZoBBol0q0KTbS8QLafYFoRIhl6jqfnkZJ1NCql5lWMAE69Ks4VlBe5
dnWZ/zQpy9yBzfoGZTfAMETUcbP/rZGKJkpW1MvwUxrX/w3MUDgBXEinNv5zxYyj
ocj7G78/5FRfGysTnd9njcSalbeoapIJaTP97199M0zNvF4lieR8Gfn1vmrbr9Oe
1MaEjTgDEO7j8zVUoJNs3FCZPVmAI4rnaMJ46qPZ/HtOgtO+JAIsVsoHsbtnvHhS
2wdcxNB++hbMyXokmbzz
=Z9SX
-----END PGP SIGNATURE-----