Implicit Communication
Implicit communication can be used in the EtherNet/IP Device Service. It is used for time-critical situations. To be as efficient as possible and to reduce bit size, implicit messaging copies data with minimal additional information.
Implicit communication is sometimes called Input/Output (I/O) messaging due to its common usage between controllers and remote I/O devices. For this, implicit communication uses Input (T2O) and Output (O2T) assemblies.
Implicit Device Profile
Implicit communication over EtherNet/IP requires specific attributes to be set within resources in the device profile. These can be found below.
Initialization Resources
Implicit communication settings must be configured in order to use implicit device resources. These configuration resources are loaded when the device service initializes.
O2T & T2O Setting Attributes
O2T and T2O settings must be configured if either is used:
| Attribute | Description | Valid Values |
|---|---|---|
| type | The type of the settings resource. Used by the device service to identify the resource type |
|
| assemblyID | The output assembly instance ID | 0 to 65536 |
| includeHeader32bit | A flag that defines whether to include a 32-bit header, which includes a run/idle notification |
|
| size | Defines the output assembly size in bytes | 0 to 2000 |
Note
T2O and O2T settings resources cannot be used for read-write operations
Configuration Settings Attributes
This resource is optional and is dependent on the Ethernet/IP device being used.
| Attribute Name | Description | Valid Values |
|---|---|---|
| type | Configuration Settings Resource Identifier, used by the device service to determine the resource type | ConfigSettings |
| assemblyID | Config assembly instance ID | 0 to 65535 |
| size | Config assembly size in bytes | 0 to 400 |
Note
Configuration settings resources cannot be used for read-write operations
Communication Device Resources
Note
The following resource can only be used if the implicit initialization resources have been set up.
Implicit Communication Device Attributes
T2O and O2T assemblies contain many values which are combined into byte arrays. Due to this, information on each resource must be included to identify the bit and byte operations needed to extract the correct value.
Use the attributes provided below in device resources to extract O2T and T2O values.
| Attribute | Description | Valid Values |
|---|---|---|
| type | Informs the device service whether it is a T2O or O2T resource |
|
| offsetBytes | Byte offset within the T2O or O2T data | 0 to 2000 |
| offsetBits | Bit offset within the O2T or T2O data | 0 to 7 |
| bitLength | Only used for 2 data types:
|
For data type:
|
Note
The maximum supported size of implicit data is 2000 bytes per device.
Implicit Protocol Properties
O2T Protocol Properties
The following O2T protocol properties are required if there is an O2TSettings device resource in the device profile:
| Property | Description | Valid Values |
|---|---|---|
| ConnectionType | Defines whether data is communicated using peer-to-peer or multicast Set to p2p to communicate using peer-to-peer Set to mcast to react in a broadcast way |
|
| RPI | The Requested Packet Interval, which is the interval in which data is exchanged | Interval in milliseconds |
| Priority | Defines the priority in which the implicit data exchange is treated |
|
| Ownership | Defines the exclusivity of the data on the target If not set to exclusive, other scanners can also establish an implicit connection to the device |
|
T2O Protocol Properties
The following T2O protocol properties are required if there is a T2OSettings device resource in the device profile:
| Property | Description | Valid Values |
|---|---|---|
| ConnectionType | Defines whether data is communicated using peer-to-peer or multicast Set to p2p to communicate using peer-to-peer Set to mcast to react in a broadcast way |
|
| RPI | The requested packet interval, which is the interval in which data is exchanged | Interval in milliseconds |
| Priority | Defines the priority in which the implicit data exchange is treated |
|
| Ownership | Defines the exclusivity of the data on the target If not set to exclusive, other scanners can also establish an implicit connection to the device |
|