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"can you give more information about what you're trying to do?"
what I want to do is to have 16 high speed transmitters that I am going to use just as high speed serializers with around 5 Gbps max rate (protocol in Basic mode, all the blocks bypassed, only a high speed serializer per channel going on). The only requirement is that I need all of them to be synchronized
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Synchronous, or synchronized?
The channels will all be synchronous, because you can use a common reference clock. However, there is no guarantee the serial data streams from transmitters are time-aligned (synchronized).
What exactly are you trying to do?
Cheers,
Dave