Explicit messaging is a way to control or query a device on an as-needed basis and is performed by PLC logic and MSG program blocks. It is necessary to detemine the Class, Instance and Attribute when using explicit messaging with the following EtherNet/IP option cards:

• GA800, GA500, HV600, and 1000 Series drives: SI-EN3, SI-EN3D, SI-EN3/V, SI-EN3D/V 
• 7 Series drives: CM092, CM093 (V7)

 

GA800, GA500, HV600, and 1000 Series Drives

For register addresses above 100H, the class is 64h.
For register addresses 100H and below, the class is 7D. 
For both classes, the Instance is the Most Significant Bit (MSB) of the address and the Attribute is the Least Significant Bit (LSB) of the address.

7 Series Drives

Refer to document TM.AFD.26 (Chapter 3 are the EtherNet/IP Objects and Chapter 5 are the Parameter Tables).

Example 1:
Accessing Frequency Reference Selection parameter b1-01 through explicit messaging

For parameter b1-01, the modbus address/register is 0180H. Because the address/register is greater than 100H, the class will be 64H, the Instance (MSB) is 01 and the Attribute (LSB) is 80.

 

Example 2:
Accessing Multi-Function Input parameter H1-05 through explicit messaging

For parameter h1-05, the modbus address/register is 0402H. Because the address/register is greater than 100H, the class will be 64H, the Instance (MSB) is 04 and the Attribute (LSB) is 02.

 

 

Example 3:
Accessing status monitor parameter U1-01 through explicit messaging

For status monitor  U1-01, the modbus address/register is 0040H. Because the address/register is LESS than 100H, the class will be 7DH, the Instance (MSB) is 01*  and the Attribute (LSB) is 40.

 

* Note: Instances of 0 are not valid in some PLCs, therefore all registers with addresses less than 100H have an Instance of 1 (For example: address 0040H will have an Instance of 1). See below for an example. 

 

Note: This information can be found Using Yaskawa's Ethernet/IP Options with ControlLogix and CompactLogix Controllers