Upload pictures and change minimum&maximum

README.md

 # fx_s1516
-
-### minimum value: -16383
-### maximum value: 16383
+![image](/uploads/f7b75bb4cbf32bcce0f5cc0ab6cfe4ec/image.png)
+### minimum value: -32768
+### maximum value: 32767.9999847
+![image](/uploads/3774c4dbf5d9d9d070b202f38a375a8c/image.png)
 ### resolution: 0.00001525878
+
+###reference: Randy Yates, Fixed-Point Arithmetic: An Introudction. pp6-pp11
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