The Modbus is commonly utilized serial protocol. It is usually practiced in a point to multi-point or point to point communication RS232. The Modbus Plus generally practiced in a multi-point to multi-point 1 Mbps RS485 network. They installed a network of Modbus plus through fiber in their plant. This lets the FIX32 to correspond with about 15 PLC Modicon. It also allocates any PLC to write or read to the other PLC in the network. It might have gone to the Modbus TCP but it had some elder 984-685E's that did not have much support for Ethernet. The Modbus Plus runs well and it continues to increase on.
The Modbus is a protocol of serial master or slave. The Modbus can work through any serial type media such as copper, fiber, wireless, modem, etc. The Modbus Plus is a protocol of peer-to-peer which operates at 1 Mbps. The protocol of Modbus Plus indicates the layer of software as well as the layer of hardware. Proprietary terminators and cabling have to be used with a network of Modbus Plus.
There are some main differences. The Modbus is maximum of 19.2Kbaud and Modbus Plus is 1Mbaud it is for all practical applications. The Modbus is an open or free protocol that utilizes standard serial connections for example RS232 or RS485 characteristically. The Modbus Plus is a network which licensed and owned by Modicon (Schneider Electric) that utilizes a Token Ring customized RS485 of two wire network design. The Modbus Plus has protocol of Modbus summarized within it message making it easy for a connection device to let the two networks to correspond with each other. For more detail you can go to the website www.modbus.org where you can find the complete specification of Modbus and some partial info on Modbus Plus. You will not discover complete information of Modbus Plus posted openly, as you require to be a alliance partner of Schneider and sign conformities with them before you are enabled to realize your hardware with this protocol. You did not request for Modbus TCP/IP with is an extra open or free network protocol that is basically the protocol of Modbus summarized in a TCP/IP Ethernet block. This protocol is very popular because it is easy and cheap to realize products that utilize the protocols, and simple to exchange between the different protocols.
Modbus is commonly used for any geographically spread systems or to connect a limited node system with incomplete data requirements. Frequently the scales or field instruments are linked point to point this technique.
Modbus Plus provides SPEED, at a price of restricted distances it is a single segment is limited to 1500 ft on RS485, longer spaces can be accomplished with repeaters and/or fiber optics. The main difference is that MB+ presents actual data volumes in real time. The network can transfer more than 2000 data words every second, while supporting PCs or programming terminals. If you perform any job you require this network.