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+# MODBUS Application Protocol SPecification V1.1b3
+
+## Introduction
+
+MODBUS is an application layer messaging protocol for client/server communication between
+devices connected on different types of buses or networks.
+
+It is currently implemented using:
+
+* TCP/IP over Ethernet. See MODBUS Messaging Implementation Guide V1.0a.
+* Asynchronous serial transmission over a variety of media (wire : EIA/TIA -232-E, EIA-422,
+EIA/TIA-485-A; fiber, radio, etc.)
+* MODBUS PLUS, a high speed token passing network.