NETWORK COMPARISONS

No one network is ideal for solving all controls problems. Table 1 shows a variety of network types and criteria. Generally there is a tradeoff between length, speed, cost, and reliability. For example, slower networks such as Controlnet/Devicenet, Lonworks, Modbus, and Profibus are designed to be highly predictable (deterministic) and work well between a central processor and distributed IO modules. Other network types such as Ethernet provide a low cost alternative for connecting IO components but it can be susceptible to electrical noise. Other network types such as Sercos are designed for motion control systems and provide outstanding interoperability between manufacturers.

Table 1: Network Comparison

Network

topology

addresses

length

speed

packet size

Bluetooth

wireless

8

10

64Kbps

continuous

CANopen

bus

127

25m-1000m

1Mbps-10Kbps

8 bytes

ControlNet

bus or star

99

250m-1000m wire, 3-30km fiber

5Mbps

0-510 bytes

Devicenet

bus

64

500m

125-500Kbps

8 bytes

Ethernet

bus, star

1024

85m coax, 100m twisted pair, 400m-50km fiber

10-1000Gbps

46-1500bytes

Foundation Fieldbus

star

unlimited

100m twisted pair, 2km fiber

100Mbps

<=1500 bytes

Interbus

bus

512

12.8km with 400m segments

500-2000 Kbps

0-246 bytes

Lonworks

bus, ring, star

32,000

<=2km

78Kbps-1.25Mbps

228 bytes

Modbus

bus, star

250

350m

300bps-38.4Kbps

0-254 bytes

Profibus

bus, star, ring

126

100-1900m

9.6Kbps-12Mbps

0-244bytes

Sercos

rings

254

800m

2-16Mbps

32bits

USB

star

127

5m

>100Mbps

1-1000bytes

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