transmission latency

Questions and discussions about the Xillybus IP core and drivers

transmission latency

Postby Guest »

Hi Eli,

One more question about the latency of data transmission.

When generating the data from IP core factory, it showed 5ms buffer.

Like this:
(FPGA to host) 32 bits 1280 MB/s Yes Data acquisition / playback (5 ms)

Not sure what does this 5ms stand for? I saw in the documents that the transmission latency of xillybus is around few microseconds instead of milliseconds.

Thanks!

Best,
Chongxi
Guest
 

Re: transmission latency

Postby support »

Hi,

This figure (5 ms in your example) is explained in the stream's edit form: It's the approximate buffering time, and it has nothing to do with latency. The help button in the edit form supplies more information, as well as this page:

http://xillybus.com/doc/xillybus-latency

By the way, a 32 bit interface has no chance of giving 1280 MB/s, because the interface uses a clock of 250 MHz at most, so there's a limit of 1 GB/s, but effectively you'll usually get something like 800 MB/s. If you're using a Revision B core, you need to make the data vector wider, or add more streams to get an aggregate bandwidth > 800 MB/s.

Regards,
Eli
support
 
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Re: transmission latency

Postby Guest »

Wow! Thank you very much for telling me that. Really helpful!

Best,
Chongxi
Guest
 


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