Modbus TCP/IP Unsolicited Data

To send unsolicited point values from a Modbus TCP/IP programmable controller to the CIMPLICITY project using the Modbus TCP/IP Communication enabler, a MSTR function block must be coded in the ladder logic. The MSTR block can send a request to write to Holding Registers in another Modbus TCP/IP slave. The Modbus TCP/IP Communication enabler uses the data portion of this message to hold a command to set a CIMPLICITY point value.

Only one project per computer can process unsolicited data and only one port within that project can perform the processing. By default, all ports are enabled for processing unsolicited data. If you have multiple Modbus TCP/IP ports on your computer, you must set the Enable/Disable Unsolicited Data global parameter to disable the unsolicited processing on all ports except the one that is designated to do the processing.

The Modbus TCP/IP Communications enabler can receive unsolicited values for points in all four device memory types (Coils, Discrete Inputs, Input Registers, and Holding Registers).

CIMPLICITY device points with the following criteria will be updated with values from the command:

The starting address of the point exactly matches the address in [Word 3] of the command,

The length of the point is less than or equal to the number of data bytes sent (as specified in [Word 4] of the command),

The point's Modbus TCP/IP device address matches that of the device sending the command

Note: You can find information on ladder logic programming and the MSTR block function in Modicon Ladder Logic Block Library User Guide (840 USE 101 00).

More information

MSTR Block Data Area Format.

Sample MSTR Block - No Timestamping.

Sample MSTR Block - Compressed Timestamping.

Sample MSTR Block - Uncompressed Timestamping.

Sample MSTR Block - Compressed Timestamping with mSecs.

Sample MSTR Block - Uncompressed Timestamping with mSecs.

Modbus TCP/IP Technical Notes.

About Modbus TCP/IP Communications.

About Modbus TCP/IP Communications.