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.
9.3.2 %S References
References in %S memory are read only.
Reference Name Definition
%S0001
FST_SCN Set to 1 when the current sweep is the first sweep.
%S0002
LST_SCN Reset from 1 to 0 when the current sweep is the last sweep.
%S0003
T_10MS
0.01 second timer contact.
%S0004
T_100MS
0.1 second timer contact.
%S0005
T_SEC
1.0 second timer contact.
%S0006
T_MIN
1.0 minute timer contact.
%S0007
ALW_ON Always ON.
%S0008
ALW_OFF Always OFF.
%S0009
SY_FULL
Set when the PLC fault table fills up. Cleared when an entry is removed
and when the PLC fault table is cleared.
%S0010
IO_FULL
Set when the I/O fault table fills up. Cleared when an entry is removed
from the I/O fault table and when the I/O fault table is cleared.
%S0011
OVR_PRE Set when an override exists in %I, %Q, %M, or %G memory.
%S0012 reserved
%S0013
PRG_CHK Set when background program check is active.
%S0014
PLC_BAT
Set to indicate a bad battery in the CPU. The contact reference is
updated once per sweep.
%S0015, 16
reserved
Program Data GFK-1503E User Manual 117
For public disclosure
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