protocolo devicenet

1. DeviceNet and SDS
Presented by :
Ramesh Vishwanathan
Biosystems and Agl. Engineering

2. Goals
 Introduction
 DeviceNet
 Smart Distributed Systems
 Comparison of DeviceNet and
SDS

3. Introduction
 An analogy –
 The Functionalities provided by CAN is
similar to Latin letters in human
communication.
 To specify a language we need a stock of
words as well as grammar to build
sentences.
 CAN users specify their own CAN-based
language, or the user decides to use a
standardized CAN-based higher-layer protocol
 Examples of CAN-based higher layer protocols
are CANopen, DeviceNet, CANKingdom,
SDC, etc.

4. DeviceNet
 DeviceNet is an application layer protocol
based on CAN 2.0A and is widely used in
industrial automation
 Originally developed by Rockwell / Allen-
Bradley and is now an “open field” bus
regulated by ODVA (Open DeviceNet
Vendors Association)
 It is an “open”, low level network that
provides connections between simple
industrial devices (such as sensors and
actuators) to higher-level devices (such
as PLC controllers and computers)
DeviceNet

5. DeviceNet
 It uses a trunk line/drop line topology that
provides separate twisted pair busses for
both signal and power distribution which
significantly reduces the amount of
hardcore wiring

6. DeviceNet
 This network allows a maximum of 64
logical nodes and supports 125, 250 and
500 Kbits/second data transfer rates
 Each module is assigned some
priorities/IDs, which are a function of the
node number (called MAC ID) and should
be unique to avoid CAN specification
violation
 Selectable end-to-end network distance
varies with speed
 125 Kbps 500 m (1,640 ft)
 250 Kbps 250 m (820 ft)
 500 Kbps 100 m (328 ft)

7. DeviceNet
 Devices can be interfaced with
network without removing power
 Supports only Standard CAN
 Uses production/consumption model for
module to module transfer
 Peer-to-Peer with Multi-Cast (one-to-many);
Multi-Master and Master/Slave
Polled or change-of-state

8. Components of DeviceNet Device

9. DeviceNet
 Each of these components are organized
into attributes, services (methods or
procedures), and behaviors of the
components
 These objects are defined by DeviceNet
specification. For instance, the identity
object has attributes such as vendor ID,
device type, and serial number.

10. DeviceNet
 A device profile consists of
 device’s object model,
 I/O data format (including definition of
assembly object(s) for efficient data
transfer and,
 the device’s configurable parameters
documented in electronic data sheet
(EDS)

11. Smart Distributed Systems (SDS)
 Developed by Honeywell's MICRO
SWITCH Division
 is also an advanced CAN based device-level
communication network bus system
for intelligent sensors and actuators
 The SDS Application Layer Protocol is
optimized for “Smart Sensors and
Actuators”, where Configuration,
Diagnostic, and Process information can
be embedded cost-effectively in a very
small footprint

12. Features of SDS
 Communication bit transfer rates are 125,
250, 500, and 1,000 kBaud
 1500 ft maximum distance at 125 kBaud
(longer with Bridge)
 Maximum of 125 modules can be
connected to the network
 12-24VDC, 2 power wires + 2
communication wires + shield
 126 logical addresses - not related to
physical location on the network
 Event-Driven, Master-Slave, Multicast and
Peer to Peer Services

13. Example
RJ45
SDS
A/D
Temp.
Substrate
RJ45
SDS
A/D
Press.
Substrate
Substrate
Use of SDS interface with state of art sensors

14. SDS
 Small and effective way to connect small
devices to a master controller.
 Master has 100% control of all modules.
 No support for communication between
modules without a master PLC.
 Supports only Standard CAN.
 Effective when it comes to connect I/O
devices (e.g., on/off switches, proximity
sensors, etc.) to a PLC, as SDS
fundamentally is a point to point
communication between a master (Host)
and remote I/O’s.

15. SDS
 SDS has 2 Special APDU (Application
Layer Protocol Data Unit) Forms:
 Short Form APDU - Shortens the CAN
message for single-bit commands such
as COS, Write, and Acknowledgement.
This allows for greater throughput and
improved system response time.
 Fragmented APDU - Allows for data
messages longer than the standard 6
data byte format. Up to 256 bytes of
data may be sent. This allows complex
data such as ASCII strings to be sent
across the network

16. Comparison
SDS DeviceNet
Possible bit rates 125k, 250k,
500k, 1M
125k, 250k, 500k
Protection
against modules
with incorrect bit
rate
Yes. No
Possible node
numbers.
0-125 0-63
Default node
number
125 63

17. Questions??