Introduction
Computers and microprocessors continue to enter every sphere of life. This fact is specifically apparent in highly automated sectors of industry. Such “artificial intellect” became more dispersed, where the necessity in a general standard to connect various devices and external networks became obvious, and led to the development of standards that will facilitate the management of controllable processes (Eisenbarth, 1998). In that regard, various standards of industrial buses were developed to connect various devices on the field level. This paper compares two industrial buses, in terms of their similarities and differences, which are the Foundation fieldbus and DeviceNet fieldbus.
Target Markets
The target market of Foundation fieldbus and DeviceNet are close to each other, in terms of their common specification for the industrial network. Nevertheless, slight differences between the markets exist, which makes each of the products more suitable for specific purposes. In that regard, due to specific optimization, Foundation fieldbuses are more suitable in industries with wet processes, and explosive environments, as well as their focus on high-end devices (Biegacki and VanGompel, 1996). Additionally, the market of Foundation fieldbuses is industries implementing process control and monitoring, i.e. “flow control, temperature control, and tank level control” (Eisenbarth, 1998).
DeviceNet, on the other hand, uses CAN (Controller Area Network) and CIP (Common Industrial Protocol), and the protocol is concerned with the logic rather than the process, i.e. “manufacturing plants, automotive, packaging, material handling” (Barlow, 2003). In that regard, the target specifications of DeviceNet are processes with simple industrial devices, such as sensors and actuators, and more complex such as drives and barcode readers (Biegacki and VanGompel, 1996). DeviceNet is more of a low-end network itself, the main tasks of which is directly connecting the devices to the control system (Biegacki and VanGompel, 1996).
Similarities
The main similarity between the two solutions, in addition to their implementation in the industrial sector can be seen in their openness to the developers and the vendors. In that regard, DeviceNet can be said to be more open, with 17 chip vendors and more than 300 product vendors, and open specifications of their buses, while Foundation buses have their chips, software and products from different vendors for H1 fieldbus and different suppliers for Ethernet components only for HSE fieldbus (High Speed Ethernet) (Synergetic Micro Systems, 1999). Other similarity can be seen in the usage of twisted pair in both standards, with DeviceNet using twisted pair for signal and power only, while Foundation fieldbuses using twisted pair in H1 protocol only. (Synergetic Micro Systems, 1999).
Differences
The first differences can be seen in the transfer rate of the protocols used in both standards, where Foundation fieldbuses H1 and HSE operate on 31.25 Kbps and 10 or 100 Mbps respectively, while DeviceNet incorporate the rates of 500, 250 or 125 kbps (Synergetic Micro Systems, 1999). The transmission rate supported in the case of DeviceNet is dependent on the length of the cable, where 500 m is the maximal distance, while in Foundation H1 fieldbuses the rate is unchangeable with maximal distance of 1900m, and in HSE this distance is 100 m for twisted pair and 2000 m for fiber. The size of the messages in both standards also differ where, DeviceNet sends 8-byte variable message, fragmenting larger packages, while Foundation’s message size is 128 octets for H1 protocol and 64 and 256 octets for HSE, in high and low priority respectively (Synergetic Micro Systems, 1999).
It should be mentioned that both fieldbuses differ, in terms of their governing standards. Foundation fieldbus H1 implements “IEC Standard 1158-2 and ISA Standard ISA S50.02” (2003), while HSE is governed by IEEE 802.3u standard. DeviceNet, on the other hand, is governed by ISO 11898 and ISO 11519 (Synergetic Micro Systems, 1999).
Works Cited
Foundation Fieldbus Overview. 2003. Web.
BARLOW, J. 2003. The Holonic Manufacturing & Controls Concept. Web.
BIEGACKI, S. & VANGOMPEL, D. 1996. The application of DeviceNet in process control. ISA Transactions. Web.
EISENBARTH, W. 1998. Using Fieldbus Technology to Integrate Automated Systems. Web.
SYNERGETIC MICRO SYSTEMS. 1999. THE SYNERGETIC FIELDBUS COMPARISON CHART. Web.