Rockwell Automation Publication 1756-PM020F-EN-P - January 2019 15
controller scoped tags is user selectable. If a tag’s External Access attribute is
set to None, then the tag cannot be accessed from outside the controller.
For more information about external access to controller scoped tags see the
Logix 5000 Controllers I/O and Tag Data Programming Manual
, publication
1756-PM004.
For more information about tags and data types, see the Logix 5000
Controllers Design Considerations Reference Manual, publication
1756-RM094.
See also
CIP data types on page 13
The Read tag, Write Tag, Read Tag Fragmented, Write Tag Fragmented, and
Read-Modify-Write Tag services require a service parameter that identifies
the data type of the tag being referenced. This tag type parameter is:
• A 16-bit value for atomic tags
• Two 16-bit values for structured tags
The value used for structures is a calculated value. For details, see Tag type
service parameters for structures.
The tag type values used for atomic tags and the resulting data size are
shown in the table shown in Tag type service parameter values used with
Logix controllers.
See also
Tag type service parameters for structures on page 38
Use this table for date types, tag type values, and size of transmitted data for
Logix controllers.
Data Type Tag Type Value Size of Transmitted Data
BOOL 0x0nc1
The BOOL value includes an additional field
(n) for specifying the bit position within the
SINT (n = 0-7).
1 byte
SINT 0x00C2 1 byte
INT 0x00C3 2 bytes
DINT 0x00C4 4 bytes
REAL 0x00CA 4 bytes
DWORD 0x00D3 4 bytes
LINT 0x00C5 8 bytes
bytes = Multi-byte data values are transmitted low-byte first
Tag type service parameter
Tag type service parameter values
used with Logix controllers
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