-Updated comment.

libraries/dsp/st/src/vhdl/st_histogram.vhd

@@ -24,6 +24,7 @@
 -- Purpose: 
 -- . Count incoming data values and keep the counts in RAM as a histogram
 -- Description: 
+--  . See st_histogram.txt for the original design description.
 --  . The contents of the inactive RAM is cleared automatically just before the
 --    next sync interval. This way, no data is lost and all valid input data
 --    contributes to the histogram. The ram_clearing status output is high