Rockwell Automation 1756-L7x GuardLogix 5570 Controllers - Manual (Page 83)

Rockwell Automation Publication 1756-UM022A-EN-P - November 2012 83
Develop Safety Applications Chapter 6
Figure 24 - Creating a New Tag
Tag Type
Table 24 defines the four types of tags: base, alias, produced, and consumed.
Table 24 - Four Tag Types
Tag Type Description
Base These tags store values for use by logic within the project.
Alias A tag that references another tag. An alias tag can refer to another alias tag or a base tag. An
alias tag can also refer to a component of another tag by referencing a member of a structure,
an array element, or a bit within a tag or member.
IMPORTANT: Aliasing between standard and safety tags is prohibited in safety applications.
Instead, standard tags can be mapped to safety tags using safety tag mapping. See
Safety Tag
Mapping on page 92 .
Produced A tag that a controller makes available for use by other controllers. A maximum of 15
controllers can simultaneously consume (receive) the data. A produced tag sends its data to
one or more consuming tags without using logic. Produced tag data is sent at the RPI of the
consuming tag.
Consumed A tag that receives the data of a produced tag. The data type of the consumed tag must match
the data type of the produced tag. The requested packet interval (RPI) of the consumed tag
determines the period at which the data updates.