ProSoft Technology MVI71-MCM - Manual (Page 27)

Installing and Configuring the Module MVI71-MCM ♦ PLC Platform
Modbus Communication Module
ProSoft Technology, Inc. Page 27 of 111
December 28, 2007
Important: The Internal Address must be used according to the Modbus function.
When using holding registers (Functions 3,6,16), or input registers (Function 4), the
Internal Address indicates the word (16 bits) address in the MVI71-MCM internal
database. For example, if using Internal Address = 500, this indicates that word 500 is
the Start Internal Address. When using bits (functions 1,2,5,15), the Internal Address
parameter indicates the bit address in the MVI71-MCM internal database. For
example, if using Internal Address = 32 and function 15, this indicates that the source
address starts at bit 0 at word 2
PollInt -
This parameter defines the minimum number of seconds to wait
between the execution of continuous commands (Enable=1). This poll interval
command can be used to lighten the communications load on a busy network.
Valid entries for this parameter are 0 through 65535.
Count - This parameter defines the number of registers to be considered by the
command. Valid entries for this parameter are 1 to 100 for functions 3, 4, and 16
and 800 for functions 1, 2, and 15. The Count parameter must be interpreted
according to the Modbus function used. Functions 1, 2, and 15: Count = Number
of Coils (1 bit). Functions 3, 4, and 16: Count = Number of Words (16 bits).
Swap -
This parameter specifies if the data used in the command must be
altered when reading data from a node on the network (Function 3). Values that
can be assigned are as follows:
0=No data swapping
1=Swap word values
2=Swap word and byte values
3=Swap byte values
This option is used when interfacing the module with ASCII and floating-point
data on other devices.
Slave Address - This parameter assigns the Modbus slave node address for the
module to reach with the command on the network. This parameter can use
values from 0 to 255. Most Modbus networks limit the upper value to 247.
Func - This parameter specifies the function to be performed by the command.
Valid entries are 1, 2, 3, 4, 5, 6, 15, and 16.
Destination Address: This parameter stores the destination address in the
slave associated with the command.
For example, if using a Read holding register function (function 3), the
Destination Address parameter will contain the address to be read in the Modbus
slave connected to a MVI71-MCM master port. If using a Write function (function
16), the Destination Address will contain the slave address to which to command
will be written.
Important: The Destination Address must be used according to the Modbus function
in the command. When using holding registers (functions 3,6,16), or input registers
(function 4), the Destination Address is expressed as the word (16 bits) address in the
slave. For example, Destination Address = 500 indicates that word 500 is the start
Destination Address. When using bits (functions 1,2,5,15,) the Destination Address
parameter is expressed as bit address in the MVI71-MCM Destination database. For
example, Destination Address = 32, with function 15, indicates that the source address
starts at the bit 0 at word 2.