Specifications

Allen-Bradley ControlLogix Ethernet Driver Help
Atomic Data
Type
Description Range
BOOL Single-bit value VT_
BOOL
0, 1
SINT Signed 8-bit value VT_UI1 -128 to 127
INT Signed 16-bit value VT_I2 -32,768 to 32,767
DINT Signed 32-bit value VT_I4 -2,147,483,648 to 2,147,483,647
LINT Signed 64-bit value VT_I8 –9,223,372,036,854,775,808 to
9,223,372,036,854,775,807
REAL 32-bit IEEE floating
point
VT_R4 1.1755 E-38 to 3.403E38, 0, -3.403E-38 to -1.1755
See Also: Logix Advanced Addressing
Client/Server Tag Address Rules
Logix tag names correspond to client/server tag addresses. Logix tag names (entered via RSLogix5000) follow
the IEC 1131-3 identifier rules. Client/server tag addresses follow these same rules. They are as follows:
l Must begin with an alphabetic (A-Z, a-z) character or an underscore (_).
l Can only contain alphanumeric characters and underscores.
l Can have as many as 40 characters.
l Cannot have consecutive underscores.
l Are not case sensitive.
Client/Server Tag Name Rules
Tag name assignment in the server differs from address assignment in that names cannot begin with an
underscore.
Note: Logix tag names should be kept to a minimum in size for optimum performance. The smaller the name, the
more requests that are able fit in a single transaction.
Important: Symbolic Mode users should keep the client/server tag addresses below 400 characters. For
example, tagarray[1,2,4].somestruct.substruct_array[3].basetag.[4] is 57 characters in length. Since a packet
can only hold 500 data bytes, any overhead bytes that need to be added to the packet can greatly diminish the
room available to the characters themselves. By keeping the address below 400, the tag request remains
complete and valid.
See Also:Performance Optimizations
Address Formats
There are several ways to address a Logix tag statically in the server or dynamically from a client. The format
used depends on the type and usage of the tag. For example, the bit format would be used when accessing a bit
within a SINT-type tag. For information on address format and syntax, refer to the table below.
Note: All formats except for Array and String are native to RSLogix5000. Therefore, when referencing an atomic
data type, an RSLogix 5000 tag name can be copied and pasted into the server's tag address field and be valid.
Format Syntax Example Notes
Standard <logix tag name> tag_1 Tag cannot be an array.
Array
Element
<logix array tag
name> [dim 1,
dim2, dim 3]
tag_1 [2, 58,
547]
tag_1 [0, 3]
Dimension range = 1
to 3 | element range = 0 to 65535
Array
w/o
Offset*
<logix array tag
name> {#
columns}
<logix array tag
name> {# rows}{#
columns}
tag_1 {8}
tag_1 {2}{4}
Dimension range = 1 to 2 | element range = 1 to 65535
The number of elements to read/write equals # of rows
times # of columns. If no rows are specified, # of rows
default to 1.
The array begins at a zero offset (array index equals 0 for
all dimensions).
Array w/
Offset*
<logix array element
tag> {# columns}
tag_1 [2, 3]
{10}
The array begins at an offset specified by the dimensions
in the array element tag. The array always covers the
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