a : AAAA AAAA AAAA AAAA (16 bits)
b : B7B6 B5B4 B3B2 B1B0 (8 bits)
+As the source is Scalar, it must be copied (broadcast) into each
+partition of the output, B, starting at the beginning of each
+partition. With each partition being smaller than A (except
+in one case) truncation is guaranteed. The exception is when
+all pattitions are open (1x) and the length of A and B are
+the same.
+
The partition options are:
| partition | o3 | o2 | o1 | o0 |