Limitations when using ControlLogix

The following known limitations exist when using the PLC mapping capability in RSLogix 5000 or Logix Designer application.
  • Do not use file numbers 0, 1, and 2. These files are reserved for Output, Input, and Status files in a PLC-5.
  • Use PLC-5 Mapping only for tag arrays of data type INT, DINT, or REAL. Attempting to map elements of system structures may produce undesirable effects.
  • Use the PLC file identifier of N or B when accessing elements in an INT tag array.
Also, the ControlLogix processor uses tags to store information instead of the file based system of the PLC and SLC processors. The use of tags allows the user to name data items in a more meaningful way, however the memory layout of the controller prevents write optimizations as the tags are not contiguous in the controllers memory. The only way to know that tags are contiguous in memory is to use an array of a simple data type, INT, DINT, SINT, REAL, or BOOLEAN, and map that array to a PLC file number. The following steps are required to optimize writes from RSView32 to ControlLogix.
  1. Create an array of a simple data type in Logix Designer.
    For example, create an array of INT[1000] and name it IntArray. Tags must be Controller scope to map to a PLC file number.
  2. Map that array to a PLC file number.
    From the Logic menu, select Map PLC/SLC Messages. Enter a file number (for example 100), and select the tag IntArray.
  3. Create a PLC topic that points to the ControlLogix in RSLinx Classic.
    In RSWho, browse to the ControlLogix, right-click and select Configure New DDE/OPC Topic. Select the Data Collection tab, and select PLC5 for Processor Type.
  4. Create tags in RSView32 using the PLC syntax.
    For example, for word 0 of the IntArray, the address in the RSView32 tag is N100:0.
This table illustrates how to reference PLC mapped data in the RSView32 tag address.
ControlLogix Array Data Type
Description
PLC File Identifier
RSView32 tag data type
INT
16-bit integer
N
Integer
DINT
32-bit integer
L
Long Integer
SINT
8-bit integer
A
Byte
REAL
floating point
F
Floating Point
BOOLEAN
value of 0, 1 or -1
B
Digital
An array of INT or DINT can be referenced in RSView32 as a boolean address. For example, the IntArray referenced as a digital tag would appear as B100:0/0. Avoid using the period to reference the bit of an array. The preferred syntax is to use the forward slash syntax from the PLC.
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