ProSoft Technology MVI71-MCM - Manual (Page 59)

Reference MVI71-MCM ♦ PLC Platform
Modbus Communication Module
ProSoft Technology, Inc. Page 59 of 111
December 28, 2007
5.2.5 Modbus Addressing
It is important to familiarize yourself with the Modbus addressing concepts when
using the MVI71-MCM module. The module supports the following address
ranges for each Modbus function:
Function Description Modbus Address Range MVI71-MCM Addressing
1 Read Output Status 0001 to 9999 bit
2 Read Input Status 10001 to 29999 bit
3 Read Holding Registers 40001 to 49999 word (16 bits)
4 Read Input Registers 30001 to 39999 word (16 bits)
5 Force Single Coil 0001 to 9999 bit
6 Preset Single Register 40001 to 49999 word (16 bits)
15 Force Multiple Coils 0001 to 9999 bit
16 Preset Multiple Registers 40001 to 49999 word (16 bits)
The table above also shows the MVI71-MCM addressing for each function.
Depending on which function is used, the database address should be
interpreted in bits or words.
Examples
MVI71-MCM as a Slave
ƒ When a Modbus master device connected to a MVI71-MCM slave port sends
a command function 5 to Modbus address 32, it will write to bit 32 in the
MVI71-MCM database (bit 0 from word 2).
ƒ When a Modbus master device connected to a MVI71-MCM slave port sends
a command function 6 to Modbus address 40032, it will write to word 32 in
the MVI71-MCM database.
MVI71-MCM as a Master
ƒ When an MVI71-MCM Master Port sends a command with the following
parameters:
Internal DB Address: 10
Count:
3
Function: 15
It will write 3 coils to the specified slave using the source bits 10, 11, 12 in the
MVI71-MCM database.
ƒ
When an MVI71-MCM Master Port sends a command with the following
parameters:
Internal DB Address: 10
Count:
3
Function: 16
It will write 3 holding registers to the specified slave using as the source words
10, 11, 12 in the MVI71-MCM database.
5.2.6 Using the Read and Write Data Areas
The MVI71-MCM module separates user data into two regions; the Read Data
area and the Write Data area. These areas must be defined inside the User Data
area. The user can set up both areas when transferring the configuration data to
the module.