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Profibus DP – CAN comparison

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CAN-DP-comparison: Baudrate

Minimum Baudrate

Default Baudrate

Maximum Baudrate

1500 kbit/s

12 Mbit/s

CAN DP

1 Mbit/s

10 kbit/s9,5 kbit/s

125 Kbit/s

Factor

1/1

1/12

1/12

1,5 Mbit/s

DP transmit telegrams with a baud rate up to 12 times higher than CAN;important, however is only the effective data transfer rate !

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CAN-DP-comparison: How do the devices communicate?

DP-Master

Slave1 Slave2 Slave3 SlaveNTemp.

5

TemperatureSensor

5

Temperaturecontrol

5

Temperaturerecorder

3

time3

clock

Sensor control

Tem

p

Tem

p

event cycle

Multimaster Master/Slave

CAN is safer than DP! Starting from 12 participants CAN is faster than DP !

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CAN-DP-comparison: Extension

MinimumExtension

AverageExtension

MaximumExtension

5000 m at 10kbit/s

CAN DP

500 m at 125 kbit/s

Factor

1 / 2,5

2,5 / 1

4 / 1

DP has a higher maximum extension than CAN at maximum Baudrate.CAN has a better maximum extension with minimum and default Baudrate.

1200m at 93,75 kbit/s bis 9,5kbit/s

200 m at 1,5 Mbit/s

40 m at 1 Mbit/s100m at 12 Mbit/s

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CAN-DP-comparison: Topology -> Line

1

2

4

3 6

5

7

8

125

9 127

126 R R

0

31

32

63

64

95

95

127

RR

CAN: This way..

or that:

1

2

4

3 6

5

7

8

125

9 127

126

R R 50 m 50 m

DP:

From 32 stations on it is: CAN can be expanded with or without repeaters. DP needs them!

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CANopen specifications according to CiA

trunklength [m]

Cable resistance[mOhm/m]

wire cross-section[mm²]

terminating resistance

[Ohm] Baudrate [kBit/s]0 .. 40 70 0,25 .. 0,34 124 1000 at 40m

40 .. 300 <60 0,34 .. 0,6 150 .. 300 >500 at 100m300 .. 600 <40 0,5 .. 0,6 150 .. 300 >100 at 500m

600 .. 1000 <26 0,75 .. 0,8 150 .. 300 >50 at 1km

DC parameters for CANopen networks for less than 64 nodes

wire cross-section[mm²] n = 32 n = 64 n = 100 n = 32 n = 64 n = 1000,25 200 170 150 230 200 1700,5 360 310 270 420 360 3200,75 550 470 410 640 550 480

Cable type

Maximum trunk length [m] (1) Maximum truk length [m] (2)

(1) Safety margin factor of 0.2 (2) Safety margin factor of 0.1

Maximum trunk length for different cable types and node numbers

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CAN-DP-comparison: Deterministics

5 5

value3

value5

3

Collisions

DP-Master

Slave1 Slave2 Slave3 SlaveNSensor control

Tem

p

Tem

p

Cycle

DP is deterministic, if there is no telegram repetitions due to transmission errors. CAN is not deterministic!

Higher priority wins!

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Profibus DP

Access method Master/Slave, Token Passing possible

deterministic

Topology Line, with repeater: Tree, Star

Media Twisted Pair shielded, fibre optics

station number 126 (31 without Repeater)

distance 2 400 m; with Repeater up to 9600 m

transmission rate 9,6 kbit/s / 19,2 / 93,75 / 187,5 / 500 / 1 500 / 12 Mbit/s

Daten size per telegram 244 Byte

data traffic cyclic (and acyclic with DP V1)

Standards EN 50170, DIN 19245 T3

Lobby Profibus User organisation (PNO) with more than 170 members a.o. Bosch,

Siemens, MOELLER, ABB

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CAN Controller Area Network

Access method CSMA/CA event/message orientated

Topology Line with short stubs

Media Twisted Pair, fibre options

Number of stations 128, Multimaster

Distance e.g. 40 m at 1 Mbit/s

up to 1 km at 50 kbit/s

max. trunk length not specified

transmission rate 10 kbit/s to 1Mbit/s

Data size per telegram 1 ... 8 Byte

data traffic acyclic

Standards ISO 11898

Lobby CiA (CAN in automation), Intel, Philips, BoschSemiconductors, Motorola, NEC, Siemens