ProSoft Technology MVI94-MCM-MHI - Manual (Page 37)

MVI94-MCM ♦ Flex I/O Platform Configuration
Serial Communications Modbus Communication Module User Manual
ProSoft Technology, Inc. Page 37 of 109
March 29, 2011
3.6.6 Node
This parameter specifies the Modbus slave node address on the network to be
considered. Values of 1 to 255 are permitted. Most Modbus devices only accept
an address in the range of 1 to 247 so be careful. If the value is set to zero, the
command will be a broadcast message on the network. The Modbus protocol
permits broadcast commands for write operations. Do not use this node address
for read operations.
3.6.7 Function Code
This parameter specifies the Modbus function to be executed by the command.
These function codes are defined in the Modbus protocol. The following table
defines the purpose of each function supported by the module.
Func Description
1 Read Coil Status
2 Read Input Status
3 Read Holding Registers
4 Read Input Registers
5 Single Coil Write
6 Single Register Write
15 Multiple Coil Write
16 Multiple Register Write
3.6.8 Device MODBUS Address
This parameter specifies the starting Modbus register or digital point address to
be considered by the command in the Modbus slave device. Refer to the
documentation of each Modbus slave device on the network for their register and
digital point address assignments.
The FC determines the addresses range and that this value will be the register or
bit OFFSET into a given data range. For example, if the command is to be a bit
command (FC 1, 2, 5, or 15) to Read/Write a Coil 0X address 00001, then the
value to enter here would be 0. For Coil address 00110, the value here would be
109. For register Read/Write commands (FC 3, 4, 6, or 16) in the 3X (FC4) or 4X
(FC3), say 30001 or 40001, the value here would, again be 0. For 31101 or
41101, the value to enter for this parameter would be 1100.