Chapter 3. Program DataGFK-2950C February 2018 393.2.2 Bit (Discrete) ReferencesType Description%I Represents input references. %I references are located in the input status table, which stores thestate of all inputs received from input modules during the last input scan. A reference address isassigned to discrete input modules using your programming software. Until a reference address isassigned, no data will be received from the module. %I memory is always retentive.%Q Represents physical output references. The coil check function checks for multiple uses of %Qreferences with relay coils or outputs on functions. You can select the level of coil checking desired(Single, Warn Multiple, or Multiple).%Q references are located in the output status table, which stores the state of the output referencesas last set by the application program. This output status table’s values are sent to output modulesat the end of the program scan. A reference address is assigned to discrete output modules usingyour programming software. Until a reference address is assigned, no data is sent to the module. Aparticular %Q reference may be either retentive or non-retentive.%M Represents internal references. The coil check function of your programming software checks formultiple uses of %M references with relay coils or outputs on functions. A particular %M referencemay be either retentive or non-retentive.%T Represents temporary references. These references are never checked for multiple coil use and can,therefore, be used many times in the same program even when coil use checking is enabled—this isnot a recommended practice because it makes subsequent trouble-shooting more difficult. %T maybe used to prevent coil use conflicts while using the cut/paste and file write/include functions.Because this memory is intended for temporary use, it is cleared on STOP Mode to RUN Modetransitions and cannot be used with retentive coils.%S%SA%SB%SCRepresent system status references. These references are used to access special CPU data such astimers, scan information, and fault information. For example, the %SC0012 bit can be used to checkthe status of the CPU fault table. Once the bit is set on by an error, it will not be reset until after thesweep. %S, %SA, %SB, and %SC can be used on any contacts.▪ %SA, %SB, and %SC can be used on retentive coils -(M)-.Note: Although the programming software forces the logic to use retentive coils with %SA, %SB,and %SC references, most of these references are not preserved across power cyclesregardless of the state of the battery or Energy Pack.%S can be used as word or bit-string input arguments to functions or function blocks.%SA, %SB, and %SC can be used as word or bit-string input or output arguments to functions andfunction blocks.For a description of the behavior of each bit, refer to System Status References.%G Represents global data references. These references are used to access data shared among severalcontrol systems.Note: For details on retentiveness, refer to Retentiveness of Logic and Data.
