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Class 1 IO Adapter

This message type defines a producer/consumer or adapter/scanner relationship between the VIM and the field device. This messaging mode defines a generic client connection, where the Logix processor (i.e., the scanner, originator) initiates the communications to the VIM (i.e., the adapter, target). 

The VIM will only accept a connection from the IP address specified in the field device for this connection. This is a security feature, to help prevent unintended control.

Figure 1 - Connection Definition Dialog with Class 1 IO Adapter Option Selected

Message Details

Select Class 1 IO Message and then select Adapter (Target Server) from the Msg Type selection in Figure 1. This will update the Msg Details section with the appropriate fields.

Assembly Instance

This value defines the connection point that the originator will use to access the data. Each connection represents one assembly instance.

Set the assembly instance to a value of from 1 to 128  (see RSLogix 5000 Class 1 ENBT Configuration, for accessing this from the Logix controller). 

Maximum RPI

The requested packet interval (RPI) may be set to a default value, however the actual RPI is determined by the IO Scanner configuration. This value is in milliseconds.

Default = 500

Exclude Output Status Bytes

The Exclude Output Status Bytes check box may be set to cause the VIM to ignore the first 4 bytes of the VIM's output buffer (Logix input buffer).  In the Logix controller these buffer bytes are used to signal the connection status, if the bits in these bytes are set (register value –1), the connection is failed (not receiving data). 

If you exclude the status bytes from the DeltaV outputs, you should set the input connection data size in Logix to be 4 bytes larger than the output connection size.  You may use this to maximize the data transport through the DeltaV datasets; all data bytes will hold data.  In this case register 1 in the DeltaV dataset not will be register 1 in the Logix.

Data Type First Register
DeltaV Logix Offset DeltaV Logix
32 bit integer w/status DINT 1 1 2
32 bit unsigned integer w/status
16 bit integer w/status INT 2 1 3
16 bit unsigned integer w/status
8 bit integer w/status SINT 4 1 5
8 bit unsigned integer w/status
Boolean w/status DINT 1 1 2
INT 2 1 3
SINT 4 1 5
Discrete w/status DINT 1 1 2
INT 2 1 3
SINT 4 1 5
Floating point w/status REAL 1 1 2
String w/status SINT 4 1 5

Table 1 - Number of Status Bytes to Exclude based on Data Type

Use Single DeltaV Buffer

This option controls how the DeltaV serial card mapping is automatically generated. When this option is enabled, and User Controls Mapping is disabled, VIMNet will use Output with Readback datasets. When this option is disabled, VIMNet will create separate Input and Output datasets.

This option is ignored if User Controls Mapping is enabled or if the VIM is emulating DeviceNet cards for this connection.

Scanner Configuration

This section determines the connection size and displays suggested IO Scanner configuration.

Comm Format

This determines the data type of the individual registers in the assembly instance. This is used in calculating the size of the connection, to determine the size (in bytes) of each transfer word.

When VIMNet Explorer is generating the DeltaV IO Card mapping, this is used to determine the data type of the dataset.

Transfer Data

This sets the number of registers in the assembly instance. It is specified in the number of registers. The data type of the register is determined by the Comm Format.

When VIMNet Explorer is generating the DeltaV IO Card mapping, this is used to determine the size of the dataset.

Input and Output Assembly Instances

The lower section of Scanner Configuration shows an example IO Scanner configuration that would match this connection definition. The values given are modeled after the Allen Bradley Logix controller. If a Logix is not the IO Scanner, these values may need to be adjusted.

Dataset Configuration

The final step for the Class 1 server is to create sufficient datasets to capture the data from the connection buffer. 

For ENBT connections to Logix controllers, it is recommended the connection be configured to match that in the client.  For a Logix controller this means you should create one or more input and output only dataset in DeltaV.  If you do not specify output w/read back, the outputs will be written to the Logix input registers for the connection, the inputs will come from the Logix output registers.  If the connection size specified in the Logix controller is more than one dataset of registers in DeltaV, multiple datasets of the IO type may be added to the DeltaV configuration to transfer the data. 

EtherNet/IP Buffer DeltaV
Type Size Dataset Size Type




1-50 1 1-50

32 bit integer w/status


Floating point w/status

51-100 1 50
2 1-50
101-135 1 50
2 50
3 1-35
INT 1-100 1 1-100 16 bit integer w/status
101-200 1 100
2 1-100
201-270 1 100
2 100
3 1-70
SINT 1-100 1 1-100 8 bit integer w/status
101-200 1 100
2 1-100
201-300 1 100
2 100
3 1-100
301-400 1 100
2 100
3 100
4 1-100
401-500 1 100
2 100
3 100
4 100
5 1-100

Table 2 - EtherNet/IP Buffer Size to DeltaV Dataset Size Mapping

EtherNet/IP Buffer to Dataset Mapping

For an ENBT connection to a Logix controller all datasets should be formatted with the same data type, because the data on the Logix is an array of a single data type. The direction may be varied depending on the processing required on the client end.

For ENBT server connections the EtherNet/IP buffer Configured box is updated automatically as datasets are added (and the dataset size is incremented).  You may add datasets until all defined buffer bytes are configured (both input and output), however this is not necessary.  If you are only writing data, then only outputs must be configured.

Datasets will use the bytes from the EtherNet/IP buffer in the order that they are defined in, e.g., the base dataset will use the first set of bytes, the second dataset will use the second set of bytes, etc. Because of this, the individual EtherNet/IP buffer map elements are not required.

See DeltaV Serial Card Mapping for more information on creating datasets. The sections defining how to map the data are not required.