08-05-2013, 03:44 PM
FOUNDATION FIELD BUS
[attachment=53606]
INTRODUCTION
Foundation Fieldbus is an all-digital, serial, two-way communications system that serves as the base-level network in a plant or factory automation environment. It is an open architecture, developed and administered by the Fieldbus Foundation. It's targeted for applications using basic and advanced regulatory control, and for much of the discrete control associated with those functions. Foundation fieldbus technology is mostly used in process industries, but nowadays it is being implemented in powerplants also.
FOUNDATION fieldbus is the only protocol with the built-in capability to distribute the control application across the network (Figure 1).
TYPES OF IMPLEMENTATION OF FF BUS
Two related implementations of FOUNDATION fieldbus have been introduced to meet different needs within the process automation environment. These two implementations use different physical media and communication speeds.
• H1 works at 31.25 kbit/s and generally connects to field devices. It provides communication and power over standard twisted-pair wiring. H1 is currently the most common implementation.
• HSE (High-speed Ethernet) works at 100 Mbit/s and generally connects input/output subsystems, host systems, linking devices, gateways, and field devices using standard Ethernet cabling. It doesn't currently provide power over the cable, although work is under way to address this.
H1 BUS
The H1 fieldbus retains and optimizes the desirable features of the 4-20 milliampere (mA) analog system such as:
• single loop integrity
• a standardized physical interface to the wire
• bus-powered devices on a single wire pair
• intrinsic safety options In addition, FOUNDATION fieldbus enables:
• increased capabilities due to full digital communications
• reduced wiring and wire terminations due to multiple devices on one wire
• increased selection of suppliers due to interoperability
• reduced loading on control room equipment due to distribution of control and input/output functions to field devices
• connection to the HSE backbone for larger systems
High Speed Ethernet (HSE)
The HSE is based on standard Ethernet technology. The required components are therefore widely used and are available at low costs. The HSE runs at 100 Mbit/s and cannot only be equipped with electrical lines, but with optical fiber cables as well. The Ethernet operates by using random (not deterministic) CSMA bus access. This method can only be applied to a limited number of automation applications because it requires real-time capability. The extremely high transmission rate enables the bus to respond sufficiently fast when the bus load is low and devices are only few. With respect to process engineering requirements, real-time requirements are met in any case. If the bus load must be reduced due to the many connected devices, or if several HSE partial networks are to be combined to create a larger network, Ethernet Switches must be used . A switch reads the target address of the data packets that must be forwarded and then passes the packets on to the associated partial network. This way, the bus load and the resulting bus access time can be controlled to best adapt it to the respective requirements.
[attachment=53606]
INTRODUCTION
Foundation Fieldbus is an all-digital, serial, two-way communications system that serves as the base-level network in a plant or factory automation environment. It is an open architecture, developed and administered by the Fieldbus Foundation. It's targeted for applications using basic and advanced regulatory control, and for much of the discrete control associated with those functions. Foundation fieldbus technology is mostly used in process industries, but nowadays it is being implemented in powerplants also.
FOUNDATION fieldbus is the only protocol with the built-in capability to distribute the control application across the network (Figure 1).
TYPES OF IMPLEMENTATION OF FF BUS
Two related implementations of FOUNDATION fieldbus have been introduced to meet different needs within the process automation environment. These two implementations use different physical media and communication speeds.
• H1 works at 31.25 kbit/s and generally connects to field devices. It provides communication and power over standard twisted-pair wiring. H1 is currently the most common implementation.
• HSE (High-speed Ethernet) works at 100 Mbit/s and generally connects input/output subsystems, host systems, linking devices, gateways, and field devices using standard Ethernet cabling. It doesn't currently provide power over the cable, although work is under way to address this.
H1 BUS
The H1 fieldbus retains and optimizes the desirable features of the 4-20 milliampere (mA) analog system such as:
• single loop integrity
• a standardized physical interface to the wire
• bus-powered devices on a single wire pair
• intrinsic safety options In addition, FOUNDATION fieldbus enables:
• increased capabilities due to full digital communications
• reduced wiring and wire terminations due to multiple devices on one wire
• increased selection of suppliers due to interoperability
• reduced loading on control room equipment due to distribution of control and input/output functions to field devices
• connection to the HSE backbone for larger systems
High Speed Ethernet (HSE)
The HSE is based on standard Ethernet technology. The required components are therefore widely used and are available at low costs. The HSE runs at 100 Mbit/s and cannot only be equipped with electrical lines, but with optical fiber cables as well. The Ethernet operates by using random (not deterministic) CSMA bus access. This method can only be applied to a limited number of automation applications because it requires real-time capability. The extremely high transmission rate enables the bus to respond sufficiently fast when the bus load is low and devices are only few. With respect to process engineering requirements, real-time requirements are met in any case. If the bus load must be reduced due to the many connected devices, or if several HSE partial networks are to be combined to create a larger network, Ethernet Switches must be used . A switch reads the target address of the data packets that must be forwarded and then passes the packets on to the associated partial network. This way, the bus load and the resulting bus access time can be controlled to best adapt it to the respective requirements.