8
SI-DeviceNet User Guide
Issue Number: 2
A fieldbus topology such as DeviceNet allows the same configuration to be realised
using only 2 signal wires plus a shield and power. This method of communication saves
significantly on the amount of cabling required and can improve overall system
reliability, as the number of inter-connections is greatly reduced.
Figure 2-2 shows a typical DeviceNet system transferring the same signals as given in
the traditionally wired example. The signals are now transmitted by converting them into
a serial data stream which is received by the master as if they were connected using
traditional wiring. The data stream on DeviceNet allows up to 56 (
28 input and 28
output
) independent values to be sent or received by the master, there are also methods
available (non-cyclic data) to allow random access to drive parameters.
Figure 2-2 DeviceNet overview
Table 2.2 Data mappings for SI-DeviceNet
Number of
network words
Type
Source / Destination
Description
1
digital inputs
slave 1 to master
status signals
digital outputs
master to slave 1
control signals
analog output
master to slave 1
control signal
digital inputs
slave 2 to master
status signals
digital outputs
master to slave 2
control signals
analog output
master to slave 2
control signal
DeviceNet master
Digital 1A Digital 1B
Digital 2A Digital 2B
Analog 1
D
ig
ita
l2
A
D
ig
ita
l2B
Di
gi
ta
l1
A
Dig
ita
l1
B
Node
1
Node
2
Analog 2
Analog 1
Analog 2
