030-iob18/README.md: explain about the fuzzer
Signed-off-by: Hans Baier <hansfbaier@gmail.com>
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# IOB18 Fuzzer
+This fuzzer solves the bits related to the IO pads in the
+high performance banks, which are present in most of the
+Kintex and Virtex devices (a notable exception are K420T and K480T)
+using bank numbers of 30 and above.
+
+These banks have a maximum voltage of 1.8V which is the reason
+why many of the BEL names end in 18 (as opposed to 33 for the
+high range banks, which run on a maximum voltage of 3.3V).
+
+Currently the focus is on supporting the most used IO standards;
+On most boards, the high performance banks are connected to DDR3
+memory and this mandates the support of single ended and differential
+SSTL15.
+Of course, all the LVCMOS variants and LVDS are a must have too.
+
+Currently unsupported are digitally controlled impedance
+(usually indicated by the regular IO standard names with a
+_DCI and _T_DCI suffix).
