Rockwell-automation Ethernet Design Considerations Reference Manual Manual de usuario descargar pdf (Pagina 72)

72 Rockwell Automation Publication ENET-RM002C-EN-P - May 2013

Chapter 4 EtherNet/IP Protocol

Explicit Messages

Explicit connections are non-time critical and are request/reply in nature.

Executing a MSG instruction or executing a program upload are examples of

explicit connections. Explicit refers to basic information (such as source address,

data type, or destination address) that is included in every message. Each request

is typically directed at a different data item. Examples of explicit applications

include the following:

• HMI

• RSLinx connections

• Message (MSG) instructions

• Program upload/download

Explicit messages use Transmission Control Protocol (TCP). Explicit messages

are used for point-to-point, client-server transactions that use transport class 3

(Class 3):

• The server side is bound to the Message Router object and has access to all

internal resources.

• The client side is bound to a client application object and must generate

requests to the server.

• Explicit messages use an explicit messaging protocol in the data portion of

the message packet.

• Explicit messages can be connected or unconnected.

An explicit message times out in 30 seconds. This is user-changeable in the

Message (MSG) instruction structure.

Application

Object

Explicit

Messaging

Connection

Request

Response

Application

Object

Explicit

Messaging

Connection

Request

Response

Device #1 Device #2

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Rockwell-automation Ethernet Design Considerations Reference Manual Manual de usuario Pagina 72