high fan out skew in v2pro

Feb 28, 2005 3 Replies

I am using v2pro 100 device with core clk speed of 200 mhz and am running rocket io, aurora and supporting logic at 156.25Mhz. I am noticing unusually high skews on these clocks. here is an excerpt from par report.


+-------------------------+----------+------+------+------------+-------------+ | Clock Net | Resource |Locked|Fanout|Net Skew(ns)|Max Delay(ns)|
+-------------------------+----------+------+------+------------+-------------+ | core_clk | BUFGMUX6S|Yes | 6096 | 1.175 |
2.654 |
+-------------------------+----------+------+------+------------+-------------+ | ssp_tx_gclk1 | BUFGMUX2S|Yes | 169 | 0.267 |
2.508 |
+-------------------------+----------+------+------+------------+-------------+ | ssp_tx_gclk2 | BUFGMUX0S|Yes | 169 | 0.158 |
2.631 |
+-------------------------+----------+------+------+------------+-------------+ | core_clk_dv2 | BUFGMUX1P|Yes | 1358 | 1.120 |
2.604 |
+-------------------------+----------+------+------+------------+-------------+ | nfclk | BUFGMUX7P|Yes | 2012 | 1.411 |
3.196 |
+-------------------------+----------+------+------+------------+-------------+ Although this skew might be for two flops which are at farthest in the chip and probably not in the path it still does seem mighty large. Is there anything we can do to reduce this skew. We are using DCM and these clock as well.

samir



+-------------------------+----------+------+------+------------+-----------
> | Clock Net | Resource |Locked|Fanout|Net Skew(ns)|Max > Delay(ns)| > +-------------------------+----------+------+------+------------+-----------

...

Proper way to address these type of issues would be to partition your design by clocks (as much as possible) and constrain each block to a dedicated area with a floor planner.

Best Regards, rudi ============================================================= Rudolf Usselmann, ASICS World Services,

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"Rudolf Usselmann" schrieb im Newsbeitrag news:d0c1ms$as$ snipped-for-privacy@nobel.pacific.net.sg...

Hmm, are these global clock nets?

Why? Arnt the global clock nets supposed to drive the WHOLE chip with low skew (full buffered etc.) ??

Regards Falk

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