Fixed a compile error.

Ethernet/W5500/w5500.h

@@ -1162,6 +1162,9 @@
  */
 #define WIZCHIP_CRITICAL_ENTER()    WIZCHIP.CRIS._enter()
 
+#ifdef _exit
+#undef _exit
+#endif
 /**
  * @brief Exit a critical section
  *

README.md

@@ -0,0 +1,18 @@
+#ioLibrary Driver
+The ioLibrary means “Internet Offload Library” for WIZnet chip. It includes drivers and application protocols. 
+The driver (ioLibrary) can be used for [W5500](http://wizwiki.net/wiki/doku.php?id=products:w5500:start) application designs. These will be updated continuously.
+
+##ioLibrary
+This driver provides the Berkeley Socket type APIs.
+- Directory Structure
+<!-- ioLibrary pic -->
+![ioLibrary](http://wizwiki.net/wiki/lib/exe/fetch.php?media=products:w5500:iolibrary_bsd.jpg "ioLibrary")
+
+- Ethernet : SOCKET APIs like BSD & WIZCHIP([W5500](http://wizwiki.net/wiki/doku.php?id=products:w5500:start), W5200 and etc) Driver
+- Internet :
+  - DHCP client
+  - DNS client
+  - Others will be added.
+
+## Revision History
+Last release : Nov. 2014