XCore Exchange

leon_heller wrote:They are written in XML. XML files can be created by the XDE.

Leon

  <Links>
    <Link Encoding="2wire" Delays="4,4">
      <LinkEndpoint NodeId="0" Link="1"/>
      <LinkEndpoint NodeId="1" Link="0"/>
    </Link>
  </Links>

Heater wrote:Have a look in the XS1-L System Specification documents. There is a section on the link protocols and switching that will gives some clues.

For example I'm sure "<Link Encoding="2wire" Delays="4,4"> is setting up a 2 wire (in each direction) serial link with 4 clocks delay between data bits and 4 clocks delay between tokens.

Still, where is the xn file actually documented?

Awesome_pants wrote: The full XN specification is in the works. It's not secret; it's just not ready yet.

The "Delays" attribute relates to the number of clock cycles between symbols and the number of clock cycles between tokens. The inter-delay (the second value) must be equal to or greater than the intra-delay (the first value). Additionally, the inter-delay cannot be 0.

Lower numbers will result in data being transmitted more quickly because the link hardware will wait fewer clock cycles between transitions. However, unless your wires are short and noise-free (e.g. on a good PCB) then you will get link errors if you try to go too fast.

The smallest value you can use is "0,1". This is what we use on the XMP board and we've seen no errors there.

When plugging XDKs together with long wiggly cables, "4,4" seems to be reliable whereas "0,1" isn't. When I wan't to be super-sure I use "15,15" (the slowest a G4 can go).

For your own hardware, you need to experiment to find the fastest speed that (a) works, and (b) you're comfortable with. "4,4" is a good starting point in most cases.