XS1-L/G External Link Differences, Compatibility, Config.

Technical discussions around xCORE processors (e.g. General Purpose (L/G), xCORE-USB, xCORE-Analog, xCORE-XA).
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XS1-L/G External Link Differences, Compatibility, Config.

Postby Heater » Fri Dec 18, 2009 5:02 pm

I've just been scanning the XS1-L and XS1-G documents with a view to understanding how to connect external links to other CPUs or FPGA etc. In particular I'm interested in getting the two wire links working at 5Mb/s and possibly 10Mb/s.

I have some concerns here:

Firstly the L and G links don't seem to be compatible with each other after. Apart from speed issues one has a HELLO token in its protocol the other does not. Is it possible to connect L and G devices together via their links?

From the XS1-L spec I see that the 2 wire link data rate is 160/S Mb/s where S is the switch clock speed. So 5Mb/s is easily achievable by slowing the switch clock. Alternatively the bit and token spacing can be stretched at the same switch clock speed to get down to 5Mb/s.

For the XS1-G devices the sec has a different statement of link speed. Where data rate is 320/x Mb/s where x is the bit spacing. There is no mention of switch speed. Is this correct? It seems impossible to get down to 5Mb/s by setting the bit spacing because the register for clocks between bits is only 4 bits wide. Is it possible to get a G device link down to 5Mb/s ?

In the tools manual I see how to configure the inter bit and inter token delays in xn files. Is it also possible to configure the switch clock from there?

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