中文摘要：

Modbus协议广泛应用于工业控制领域，但其在实践中存在通信安全性差和效率低的问题。对此。分别对协议进行了“身份认证”与“读离散寄存器”功能码扩展。“身份认证”通过区分操作权限，保证通信安全；“读离散寄存器”支持对不连续地址寄存器的访问，提高了通信效率及协议寻址地址分配的灵活性。在基于RS．485的某太阳能光伏发电控制网络中成功应用的实例表明，扩展功能可有效提高协议的通信安全性与效率。

英文摘要：

Modbus protocol has been widely applied in industrial control field, but the problems of poor communication security and low efficiency are existed in practice. Therefore the function codes of ＂ID authentication＂ and ＂read discrete register＂ in the protocol are expanded. By distinguishing the operated authentication, the ＂ID authentication＂ ensures the communication safety; the ＂read discrete register＂ supports the access to registers with the discontinuous addresses, thus the communication efficiency and the flexibility of addressing assignment for protocol are improved. The successful application in RS-485 based control network of certain solar photovoltaie power generation shows that the security and the efficiency of the communication can be effectively improved by the extended functions.