ControlLogix Data Types

Overview

The ControlLogix driver in ACM supports multiple data types associated with tags in the device. The following sections outline all the types and their descriptions.

Type	CIP Type	Description
BOOL	C1	Boolean/Digital. To invert the display value of a Boolean tag, use the following format: Tagname! – Will display the inverse of the actual value.
SINT	C2	8-Bit Integer
INT	C3	Signed 16-Bit Integer
DINT	C4	Signed 32-Bit Integer
LINT	C5	Signed 64-Bit Integer
USINT	C6	Unsigned 8-Bit Integer (Model/Firmware Dependent)
UINT	C7	Unsigned 16-Bit Integer (Model/Firmware Dependent)
UDINT	C8	Unsigned 32-Bit Integer (Model/Firmware Dependent)
REAL	CA	32-Bit Float
LREAL	CB	8 Byte Real (Model/Firmware Dependent)
DWORD	D3	The protocol supports reading and writing values to D3 indexed arrays. The protocol handles calculating the correct offset within the DWORD, so tag access works the same way arrays are described below. Requests for index values residing within the same base DWORD index are consolidated to minimize traffic by reducing the number of redundant service requests.
Micro 800 String	DA	(Model/Firmware Dependent)
STRING	0	See String Support Section. Strings that are listed get stored with a CIP type of 0.

String Support

The protocol handles STRING tags within the device as a single tag. The OPC item for a STRING tag will display the concatenated contents of the character array stored in the device using the following rules for termination of the last character:

The first NULL character encountered.
The LEN parameter value if 1 has not occurred.
End of the array if 1 or 2 have not occurred first.

The protocol will update the LEN parameter on writes unless disabled by option. The user can also disable use of LEN while reading strings by option. Please refer to Configuration.

Array Support

The protocol supports reading and writing values to indexed arrays. During a tag discovery poll, any array structured tags will be identified with an OPC item placeholder in the following format:

tagname[0] - indicates a one dimensional array
tagname[0,0] - indicates a two dimensional array
tagname[0,0,0] - indicates a three dimensional array

To access the third logical element in a one dimensional array of a tag called MyArrayTag the user would alter the OPC item name to MyArrayTag[2].

Bit Offset Support

Integer bit offsets are supported for read operations only on 16 and 32 bit integer data types. To access a bit offset, use the following format:

Tagname/2 – To access the third position (zero based) bit as a Boolean

Requests for index values residing within the same Integer tag are consolidated to minimize traffic by reducing the number of redundant service requests. To invert the display value of a Bit Offset tag, use the following format:

Tagname/2! – Will display to logical inverse of the actual value. Writes to this tag will be the logical inverse of the actual value.