GLCKs on Spartan3

Jul 28, 2005 3 Replies

Hi everyone,



in my design on a Spartan3 there are 9 GCLKs used, but there are only 8 available. Is the number of GCLKs related to the BUFG, or where can I change the design to use fewer of these global clocks. (I'm just using one single system clock at 100 MHz, but some BUFGs for DCMs, but not too much). Anyone can help?



Thanks in advance,



Stefan


Stefan,

You cannot have 9 GCLKs, as S3 has only 8, yet there are only 8 BUFGs. You may have a limitation of interconnect between DCMs and respective BUFGs.

Can you explain a bit more?

Vladislav

Hi Vladislav,

now I solved my problem: I used 4 DCMs (2 BUFGs each), but I thought it were only 3 (copy and paste mistake at own IPs). That's why I run out of BUFGs.

BUFGs.

single

Glad it worked out for you. In case you run out of BUFGs in the future, you may want to use local clocks if some of the clocks only drive a small amount of logic.

Jim

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