Improve description of C opcode map

1 files changed, 3 insertions, 1 deletions

diff --git a/src/c.tex b/src/c.tex
index 1f4869e..912b082 100644
--- a/src/c.tex
+++ b/src/c.tex
@@ -1215,7 +1215,9 @@ HINTs will ever be defined in this subspace.
 \section{RVC Instruction Set Listings}
 
 Table~\ref{rvcopcodemap} shows a map of the major opcodes for RVC.
-Opcodes with the lower two bits set correspond to instructions wider
+Each row of the table corresponds to one quadrant of the encoding
+space.  The last quadrant, which has the two
+least-significant bits set, corresponds to instructions wider
 than 16 bits, including those in the base ISAs.  Several instructions
 are only valid for certain operands; when invalid, they are marked
 either {\em RES} to indicate that the opcode is reserved for future