Gateway 312785C About DeviceNet, Predefined Master/Slave Connection Set, Level of Support

Appendix A: DeviceNet™ Slave Communication

About DeviceNet

DeviceNet is a connection-based network. In this con- text the term connection refers to a communication path between two or more devices, and not the physical (cable) connection to the DeviceNet network. A connec- tion must be established between two devices in order to transfer data.

There are two types of connection defined by the Devi- ceNet specification. Each has different characteristics and is suited to a specific type of communication.

•I/O Connection – Dedicated data transfer between a producer and one or more consumers. The format of the data is known or implied by the connection.

•Explicit Messaging – Generic multi-purpose mes- saging connection, typically command and response message commands.

Each connection type has an extensive number of parameters, which can affect the characteristics of the communication path. For many Master/Slave communi- cations scenarios, a defined set of connections, together with their respective parameter settings exist under the collective name Predefined Master/Slave Connection Set. Many of the steps involved in creating and configur- ing a connection have been removed with this connec- tion set, thus simplifying the network configuration.

Predefined Master/Slave Connection Set

The DeviceNet specification details a number of con- nections that facilitate data transfer between a Master and Slave devices. The following sections detail the con- nection types supported by the Gateway.

•I/O Bit-Strobe Connection: The Bit-Strobe connec- tion is an I/O connection over which Bit-Strobe I/O command and response messages are transferred. The Bit-Strobe command is broadcast by the Master device and is received by all slave devices simulta- neously. The command message contains a single bit of information for each slave on the network. Each slave device is required to respond with a Bit- Strobe response message. The response message can contain up to 8 bytes of information.

•I/O Poll Connection: The Poll connection is an I/O connection over which Poll command and response messages are transferred. The Poll command is transmitted by the master, and is directed to a single slave device. The slave device in turn responds with a Poll response message. Both the Poll command and Poll response messages can contain any num- ber of bytes.

•I/O Data Connection: The I/O Data connection is part of the Predefined Master/Slave Connection Set, but instead is included for devices, which support creating I/O data connections via the UCMM (Unconnected Message Manager).

Level of Support

The Gateway provides Group 2 Server level support: A UCMM capable device that is configured to act as a Slave for the Predefined Master/Slave connection set.

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