Bit (Discrete) References - GE PACSystems RXi User Manual

Chapter 7. CPU Program Data
7.2.2

Bit (Discrete) References

Type
%I
%Q
%M
%T
%S
%SA
%SB
%SC
%G
Note:
128
Represents input references. %I references are located in the input status table, which stores
the state of all inputs received from input modules during the last input scan. A reference
address is assigned to discrete input modules using your programming software. Until a
reference address is assigned, no data will be received from the module. %I memory is always
retentive.
Represents physical output references. The coil check function checks for multiple uses of %Q
references 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
references as last set by the application program. This output status table's values are sent to
output modules at the end of the program scan. A reference address is assigned to discrete
output modules using your programming software. Until a reference address is assigned, no
data is sent to the module. A particular %Q reference may be either retentive or non-retentive.
Represents internal references. The coil check function of your programming software checks
for multiple uses of %M references with relay coils or outputs on functions. A particular %M
reference may be either retentive or non-retentive.
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 is not a recommended practice because it makes subsequent trouble-shooting
more difficult. %T may be 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-to-Run transitions and cannot be used with retentive coils.
Represent system status references. These references are used to access special CPU data
such as timers, scan information, and fault information. For example, the %SC0012 bit can be
used to check the status of the Controller Fault table. Once the bit is set on by an error, it will
not be reset until after the sweep.
■
%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
cycles, regardless of the state of the 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
and function blocks.
For a description of the behavior of each bit, refer to Section 7.7, System Status References.
Represents global data references. These references are used to access data shared among
several control systems.
For details on retentiveness, refer to Section 7.5 Retentiveness of Logic and Data.
PACSystems* RXi Distributed IO Controller User Manual
Description
GFK-2816F