Wiring of the DeviceNet Network

Overview

This chapter describes how to connect the LTMR controller to a DeviceNet network with an open-style connector.

It presents an example of DeviceNet network topology and list cable specifications.

WARNING
LOSS OF CONTROL The designer of any control scheme must consider the potential failure modes of control paths and, for certain critical functions, provide a means to achieve a safe state during and after a path failure. Examples of critical control functions are emergency stop and overtravel stop. Separate or redundant control paths must be provided for critical control functions. System control paths may include communication links. Consideration must be given to the implications of anticipated transmission delays or failures of the link.⁽¹⁾ Each implementation of an LTMR controller must be individually and thoroughly tested for proper operation before being placed into service. Failure to follow these instructions can result in death, serious injury, or equipment damage.

WARNING

LOSS OF CONTROL

The designer of any control scheme must consider the potential failure modes of control paths and, for certain critical functions, provide a means to achieve a safe state during and after a path failure. Examples of critical control functions are emergency stop and overtravel stop.
Separate or redundant control paths must be provided for critical control functions.
System control paths may include communication links. Consideration must be given to the implications of anticipated transmission delays or failures of the link.⁽¹⁾
Each implementation of an LTMR controller must be individually and thoroughly tested for proper operation before being placed into service.

Failure to follow these instructions can result in death, serious injury, or equipment damage.

(1) For additional information, refer to NEMA ICS 1.1 (latest edition), Safety Guidelines for the Application, Installation, and Maintenance of Solid State Control.

DeviceNet Network Characteristics

Overview

The LTMR DeviceNet controller complies with the standard DeviceNet specification.

Physical Layer

DeviceNet’s data link layer is defined by the CAN (Controller Area Network) specification and by the implementation of widely available CAN controller chips. CAN also implements a differentially driven (common return), two-wire bus line.

DeviceNet’s physical layer contains two twisted pairs of shielded wires. One twisted pair is for transferring data and one is for supplying power. This results in simultaneous support for devices that receive power from the network (like sensors) and those that are self-powered (like actuators). Devices can be added or removed from the bus line without powering down the fieldbus.

Network Topology

DeviceNet supports a trunk line/drop line network configuration. The implementation of multiple, branched, zero, and daisy chained drops should be established during system design.

The maximum number of secondaries connected to one primary is 63.

The network must be terminated at each end with 120 Ω resistors.

A sample DeviceNet network topology is shown in the following figure:

1 Trunk line

2 Drop line (0...6 m / 0...20 ft)

3 Daisy chain drop-off

4 Branched drop-off

5 Network node

6 Trunk line tap junction

7 Terminating resistor

8 Zero drop

9 Short drops

Transmission Media

Your implementation of thick, thin, or flat cables for trunk lines and drop lines should be established during system design. Thick cables are generally used for trunk lines. Thin cables can be used for trunk or drop lines.

Maximum Network Lengths

End-to-end network distance varies with data rate and cable size. The following table shows the range of bauds that the Controller supports for CAN devices and the resulting maximum length of the DeviceNet network.

Cable Type	125 kBaud	250 kBaud	500 kBaud
Thick Trunk	500 m (1,640 ft)	250 m (820 ft)	100 m (328 ft)
Thin Trunk	100 m (328 ft)	100 m (328 ft)	100 m (328 ft)
Flat Trunk	420 m (1,378 ft)	200 m (565 ft)	75 m (246 ft)
Maximum Drop Length	6 m (20 ft)	6 m (20 ft)	6 m (20 ft)
Cumulative Drop Length (sum of the length of all drop lines)	156 m (512 ft)	78 m (256 ft)	39 m (128 ft)

Network Model

Like any broadcast communications network, DeviceNet operates within a producer/consumer model. Each data packet’s identifier field defines the data priority and allows for efficient data transfer among multiple users. All nodes listen on the network for messages with identifiers that apply to their functionality. Messages sent by producer devices are accepted only by designated consumer devices.

DeviceNet supports polled, cyclic, change of state, and explicit data exchange.

DeviceNet allows users to implement a primary/secondary, or multi-primary network architecture (or some combination thereof), depending on the device’s flexibility and your application requirements.

For more information, refer to Using the DeviceNet Communication Network.

DeviceNet Communication Port Wiring Terminal Characteristics

Physical Interface and Connector

The LTMR Controller front face is equipped with one open-style, pull-apart, terminal block for DeviceNet communication.

The DeviceNet communication drivers are powered internally.

Open-Style Terminal Block

The LTMR controller has the following DeviceNet network plug-in terminals and pin assignments.

Pin	Signal	Description
1	V+	Not connected
2	CAN_L	CAN_L bus line (high dominant)
3	S	Shield
4	CAN_H	CAN_H bus line (low dominant)
5	V-	Ground

Open-Style Terminal Block Characteristics

Connector	5 pins
Pitch	5.08 mm (0.2 in.)
Tightening torque	0.5...0.6 N•m (5 lb-in)
Flat screwdriver	3 mm (0.10 in.)

Wiring of the DeviceNet Network

Overview

This section describes the connection of LTMR controllers installed in withdrawable drawers.

DeviceNet Wiring Rules

The following wiring rules must be respected in order to reduce disturbance due to EMC on the behavior of the LTMR controller:

Keep a distance as large as possible between the communication cable and the power or control cables (minimum 30 cm or 11.8 in.).
Cross over the DeviceNet cables and the power cables at right angles, if necessary.
Install the communication cables as close as possible to the grounded plate.
Do not bend or damage the cables. The minimum bending radius is 10 times the cable diameter.
Avoid sharp angles of paths or passage of the cable.
Use the recommended cables only.
A DeviceNet cable must be shielded:
- The cable shield must be connected to a protective ground.
- The connection of the cable shield to the protective ground must be as short as possible.
- Connect together all the shields, if necessary.
- Perform the grounding of the shield with a collar.
When the LTMR controller is installed in a withdrawable drawer:
- Connect together all the shield contacts of the withdrawable drawer part of the auxiliary connector to the ground of the withdrawable drawer to create an electromagnetic barrier. Refer to the Okken Communications Cabling & Wiring Guide (available on request).
- Do not connect the cable shield at the fixed part of the auxiliary connector.
Place a line terminator at each end of the bus to avoid malfunctions on the communication bus. A line terminator is already integrated in the primary.
Wire the bus between each connector directly, without intermediate terminal blocks.
The common polarity (0 V) must be connected directly to protective ground, preferably at one point only for the entire bus. In general, this point is chosen either on the primary device or on the polarization device.

For more information, refer to the Electrical Installation Guide (available in English only), chapter ElectroMagnetic Compatibility (EMC).

NOTICE
COMMUNICATION MALFUNCTION Respect all the wiring and grounding rules in order to avoid communication malfunctions due to EMC disturbance. Failure to follow these instructions can result in equipment damage.

LTMR Controllers Installed in Withdrawable Drawers

The wiring diagram for connection of LTMR controllers installed in withdrawable drawers to the DeviceNet bus is as follows:

1 Primary (PLC, PC, or communication module) with line terminator

2 DeviceNet shielded cable

3 Grounding of the DeviceNet cable shield

4 Withdrawable drawer

5 Withdrawable drawer part of the auxiliary connector

6 Fixed part of the auxiliary connector

7 Line terminator VW3 A8 306 DR (120 Ω)