Operating instructions

Modifying the Configuration File PTQ-MCM ♦ Quantum / Unity Platform
Modbus Communication Module
ProSoft Technology, Inc. Page 71 of 139
April 29, 2008
Parameter Description
Poll Interval
The minimum delay to be applied between consecutive polls for this
command. Enter this number as milliseconds.
Reg Count
Register count. Enter the number of bits or words for this command. The
maximum value for word commands (3, 4, 6 and 16) is 125 words. The
maximum value for word commands (1, 2, 5 and 15) is 800 bits.
Swap Code
This value configures if the data bytes and words should be swapped. The
possible values are:
Swap
Code
Description
0 None - No Change is made in the byte ordering (1234 = 1234)
1 Words - The words are swapped (1234=3412)
2
Words & Bytes - The words are swapped then the bytes in
each word are swapped (1234=4321)
3 Bytes - The bytes in each word are swapped (1234=2143)
Node Address
The slave address to which the command will be sent. This parameter can be
assigned numbers from 2 to 255.
Modbus Function
The following modbus functions are supported:
1- Read Coil Status (bit)
2- Read Input Status (bit)
3- Read Holding Registers (word - 16 bits)
4- Read Input Registers (word - 16 bits)
5- Force Single Coil (bit)
6- Preset Single Register (word - 16 bits)
15- Force Multiple Coils (bit)
16- Preset Multiple Registers (word - 16 bits)
MB Address in
Device
This parameter defines the starting address in the device being considered
by the command. Values entered in this field are dependent on the node's
database definition. Refer to the specific manufacturer's database definition
for the device to determine the location of the data to be interfaced.
ENRON Floating Point Support
Many manufacturers have implemented special support in their drivers to support
what is commonly called the Enron version of the MODBUS protocol. In this
implementation, register addresses > 7000 are presumed to be floating point
values. The significance to this is that the count field now becomes a 'number of
values' field. In floating point format, each value represents two words.
Configuring the Floating Point Data Transfer
A common question when using the module as a Modbus Master is how floating
point data is handled. This really depends on the slave device and how it
addresses this application.
Just because your application is reading/writing floating point data, does not
mean that you must configure the Float Flag, Float Start parameters within the
module.
These parameters are only used to support what is typically referred to as Enron
or Daniel Modbus, where one register address must have 32 bits, or one floating
point value. Below is an example: