# Reg:Tags\_demo.cc example

**URL:** <https://www.ruby-forum.com/t/reg-tags-demo-cc-example/227337>\
**Category:** GNU Radio\
**Created:** [March 12, 2013, 3:54am UTC](https://www.ruby-forum.com/t/reg-tags-demo-cc-example/227337 "2013-03-12T03:54:09Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![john\_old](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9f8e36/32.png) [@john\_old](https://www.ruby-forum.com/u/john_old)\
**Post date:** [March 12, 2013, 3:54am UTC](https://www.ruby-forum.com/t/reg-tags-demo-cc-example/227337/1 "2013-03-12T03:54:09Z")

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Hi,

1. What is get\_full\_seconds and get\_frac\_seconds printing?

2.Can we get upto precision of nano seconds using the above methods and  
please tell me how to do it.  
In the frac seconds i am getting 0.xxxxxx(only 6 digits after  
point-micro  
seconds)

Thanks

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<div class="post-metadata">

**Author:** ![john\_old](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9f8e36/32.png) [@john\_old](https://www.ruby-forum.com/u/john_old)\
**Post date:** [March 12, 2013, 7:23pm UTC](https://www.ruby-forum.com/t/reg-tags-demo-cc-example/227337/2 "2013-03-12T19:23:51Z")

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On 03/11/2013 09:52 PM, john jade wrote:

> Hi,
> 
> 1. What is get\_full\_seconds and get\_frac\_seconds printing?

Its probably the receive timestamp, its the time stamp from this object:

[http://files.ettus.com/uhd\_docs/doxygen/html/classuhd\_1\_1time\_\_spec\_\_t.html](http://files.ettus.com/uhd_docs/doxygen/html/classuhd_1_1time __spec__ t.html)

> 2.Can we get upto precision of nano seconds using the above methods and  
> please tell me how to do it.

The fractional seconds are stored as double precision floating point.  
This gives the fractional seconds enough precision to unambiguously  
specify a clock-tick/sample-count up to rates of several petahertz.

-josh

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<div class="post-metadata">

**Author:** ![john\_old](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9f8e36/32.png) [@john\_old](https://www.ruby-forum.com/u/john_old)\
**Post date:** [March 12, 2013, 8:41pm UTC](https://www.ruby-forum.com/t/reg-tags-demo-cc-example/227337/3 "2013-03-12T20:41:32Z")

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On 03/12/2013 02:14 PM, Josh B. wrote:

> > 2.Can we get upto precision of nano seconds using the above methods and  
> > please tell me how to do it.  
> > The fractional seconds are stored as double precision floating point.  
> > This gives the fractional seconds enough precision to unambiguously  
> > specify a clock-tick/sample-count up to rates of several petahertz.  
> > Although time can be _represented_ with petahertz+ resolution, doesn’t  
> > the hardware clock constrain the _realizable_ resolution? For example on  
> > a USRP with a 100 MHz FPGA clock, would actual transmit precision be  
> > limited to 10 ns?

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<div class="post-metadata">

**Author:** ![john\_old](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9f8e36/32.png) [@john\_old](https://www.ruby-forum.com/u/john_old)\
**Post date:** [March 12, 2013, 9:41pm UTC](https://www.ruby-forum.com/t/reg-tags-demo-cc-example/227337/4 "2013-03-12T21:41:11Z")

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On 03/12/2013 02:36 PM, Sean Nowlan wrote:

> > > 2.Can we get upto precision of nano seconds using the above methods and  
> > > please tell me how to do it.  
> > > The fractional seconds are stored as double precision floating point.  
> > > This gives the fractional seconds enough precision to unambiguously  
> > > specify a clock-tick/sample-count up to rates of several petahertz.  
> > > Although time can be _represented_ with petahertz+ resolution, doesn’t  
> > > the hardware clock constrain the _realizable_ resolution? For example on  
> > > a USRP with a 100 MHz FPGA clock, would actual transmit precision be  
> > > limited to 10 ns?

The resolution as to which clock tick an event would happen at is only  
as fine as the clock you are using. -josh