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E3X-DRT21-S
User’s Manual
Section 3
Explicit Message Communications
Explicit Message Communications
Sending a DeviceNet Explicit message from the master to the Communication Unit
enables reading and writing any parameters of the specified sensor. The Communication
Unit processes the command sent from the master and then returns a response.
Basic Format of Explicit Messages
The basic format of each command and response is shown below:
●
Command Format
[Destination Node Address]
Specify a node address of the unit that an Explicit message (command) is sent to. The
node address must be a single byte in hexadecimal.
[ServiceCode], [Class ID], [Instance ID], [Attribute ID]
These are parameters to specify a command type, process target, and process
details.
The Communication Unit uses the [Instance ID] to specify to sensors for which the
command is intended (Sensor unit number.) Some commands do not require an
[Attribute ID].
Depending on the master, each length of [Class ID], [Instance ID], and [Attribute ID] might be
different. When a message is sent from an Omron DeviceNet master, specify a [Class ID] and an
[Instance ID] in two bytes as four digits, and an [Attribute ID] in a single byte as two digits.
[Data]: Data is not required when using a Read command.
●
Response Format
• Normal
• Failure
[Number of Received Bytes]
The number of the received data starting from the [Source Node Address] is returned
in hexadecimal. When an error response is returned to the Explicit message, the value
always will be 0004Hex.
[Source Node Address]
The node address of the node that sent the command is returned in hexadecimal.
Destination Node Address
Service Code
Class ID Instance ID Attribute ID Data
Number of Received Bytes
Source Node Address
Service Code
Data
Number of Received Bytes: 0004Hex (Fixed) Source Node Address
Service Code Error Code
