At a Glance

That example deals with 2 Modicon M340 processors which communicate via Modbus serial link.

Description of the Example

The following example uses unlocated variables, and covers the writing of an unlocated 50-word table named Tab_1 (declared as an ARRAY [0..49] OF INT) in the Modbus slave. The management parameters are located in a table of 4 integers called Management_Parameter (declared as ARRAY [0..3] OF INT).

In that example, the Modbus slave’s number is 7, so the input ADDM parameter is ‘0.0.0.7’:

• 0: rack number of the processor equal to 0

• 0: slot number of the processor within the rack, equal to 0 as the slot number of a Modicon M340 processor is always 0

• 0: channel number, equal to 0 as the serial link of a Modicon M340 processor is always channel 0

• 7: configured slave number is 7.

The values to write are in the variable Tab_1 of the sender.

Illustration

The two Modicon 340 processors are connected via a Modbus link:

Programming

Programming in ST:

IF RE(%I0.3.1) AND NOT Management_Parameter[0].0 THEN 

   WRITE_VAR(ADDM(’0.0.0.7’),’%MW’,0,50,Tab_1,Management_Parameter);

END_IF;

The request parameters are as follows: