Assignment of Modbus ports

The Modbus port configuration screen can be used to select the Modbus communication parameters for 3 ports: ports No. 1, 2 and 3.

Port No. 1 is assigned:

  • to the built-in Modbus port for 140 CPU 6•• processors

  • to the first built-in Modbus port (MODBUS COMM1) for other Quantum processors

Port No. 2 is assigned:

  • either to the second built-in port (MODBUS COMM2), for processors with 2 built-in ports

  • or to one or several NOM modules.

Port No. 3 is assigned: to one or several NOM modules

Rule for assignment of ports 2 and 3 to NOM modules:

Starting with the lowest slot numbers:

  • the first NOM module will be assigned to port 2,

  • the second will be assigned to port 3,

  • the third will be assigned to port 2,

  • the fourth will be assigned to port 3,

  • the fifth will be assigned to port 2,

  • the sixth will be assigned to port 3.

Note: It is possible to change the assignment order of 2 of them by entering

their slot number in the Head Slot column (see table below).

Important:

The port parameters are only taken into account if the switches on the front panels of Quantum 140 CPU 3••/4••/5•• processors (used with first built-in port MODBUS COMM1) and of NOM modules are in the Mem position.

Access to the configuration editor

Carry out the following actions:

Step

Action

1

Select the processor and then select the Open module command from the popup menu.

2

Select the Modbus Port tab.

Result: The following screen appears:

Presentation of configuration parameters

Carry out the following actions:

Step

Action

1

Choose the operating mode: Bridge Mode checkbox

2
Choose the transmission speed:

3
Choose the number of Stop bits:

4
Choose the parity:

5

Choose the Delay which corresponds to the minimum time tolerated between two frames, also called delay between frames.

6

Choose the Modbus port slave address.

7

By default, if the Head Slot fields are left set to 0, the NOM modules observe the normal assignment rule described above.

Entering the slot number of a NOM module assigns it to the corresponding port (the assignment rule is no longer applied for this module but continues to apply to other modules).

8
Choose the communication mode:

9
Choose the communication protocol: