Setup
Document No. D106-009
Page 33 of 76
Revision 1.15
Modbus read and write functions involve the transfer of either Booleans or integers (16 bit).
A part or combination of integers may represent other types. For this reason, the Modbus
Router allows the mapping of integer based functions to the following data types when using
the MicroLogix/SLC controller:
BOOL
INT
REAL
All discrete or Boolean based function need to be mapped to a BOOL array (eg. B3:0).
NOTE
: When mapping a range of registers to a File array, it is important to
ensure that the destination File array is sufficiently large to accommodate all
the data.
NOTE
: When mapping a range of registers to a Float File array, the Register
Start must be an even number, else the integer data will not be aligned with
the 32-bit destination Float File.
NOTE
: When writing to a REAL datatype the user cannot write a single Modbus
element (16-bit). At least two elements will need to be written a float datatype.
NOTE
: When doing a single/multiple coil/discrete write to a MicroLogix/SLC
Bool array datatype the remaining bits of the 32-bit aligned Bool array will be
overwritten.
Next the range of Modbus data to be accessed must be specified. This is achieved by selecting
a
Register Start
and
Element Count
.
If the Modbus
Element Count
is 1, it is possible to map a single integer register to a single
integer tag. All other combinations will require a File array to be selected.
Below is an example of the target File selection. The File must be entered manually by typing
in the needed File (eg. N7:20).