Table of Contents
Advertisement
User Manual
GFK-1503F
The last time a %Q or %M reference is used with a coil, the coil type determines whether
the data is retentive or non-retentive. For example, if %Q0001 was last programmed as the
reference of a retentive coil, the %Q0001 data is retentive.
However, if %Q0001 was last programmed on a non-retentive coil, then the % Q0001 data
is non-retentive.
•
%Q or %M references that have been made retentive by specifically declaring them to
be retentive. %Q and %M references default to nonretentive.
The following data is non-retentive:
•
The states of transition coils.
•
%T data
•
%S, %SA, and %SB data (but %SC bit data IS retentive)
•
%Q and %M references that have not been declared to be retentive.
•
%Q and %M references that are used with non-retentive coils:
9.3
System Status References
The PLC stores system status data in predefined references in %S, %SA, %SB, and %SC
memory. Each system status reference has a descriptive name. For example, time tick
references are named T_10MS, T_100MS, T_SEC, and T_MIN. Examples of convenience
references include FST_SCN, ALW_ON, and ALW_OFF.
9.3.1
Using the System Status References
System status references can be used as needed in application programs. For example, the
following function block uses the FST_SCN (first scan) status reference to control power flow
to a Block Clear function. In this example, at powerup, 32 words of %Q memory (512 points)
beginning at %Q0001 are filled with zeros.
Figure 56
Program Data
-( )- coils
—
-(/)- negated coils
—
-(S)- SET coils
—
-(R)- RESET coils
—
Chapter 9
Jan 2020
93
Advertisement
Table of Contents
