[Discuss-gnuradio] The use of scrambler/ descrambler blocks

Some years ago I implemented a scrambler block in FPGA for a transmitter. It produced an output every clock cycle. 

Now I try the GNU Radio scrambler/descrambler blocks. They work great if the data flows continously like from a Vector source or File.

However if I have a discontinous source like a text message or a TCP/IP Source, the scrambler got stuck and has no output. In others words I need something analogous to a CLOCK for discontinous sources.

How to achieve that? Maybe XORing the discontinous source with a source of 0's produced at "sample rate"?

 Thanks for your time.