Filter
Top Products
2-24 Series 90-30/20/Micro Programmable Controllers Reference Manual
–
September 1998 GFK-0467K
2
System Status References
System status references in the Series 90 PLC are assigned to %S, %SA, %SB, and %SC memory.
They each have a nickname. Examples of time tick references include T_10MS, T_100MS,
T_SEC, and T_MIN. Examples of convenience references include FST_SCN, ALW_ON, and
ALW_OFF.
Note
%S bits are read-only bits; do not write to these bits. You may, however, write to
%SA, %SB, and %SC bits.
Listed below are available system status references, which may be used in an application program.
When entering logic, either the reference or the nickname can be used. Refer to chapter 3, “Fault
Explanations and Correction,” for more detailed fault descriptions and information on correcting
the fault.
You cannot use these special names in another context.
Table 2-6. System Status References
Reference Nickname 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 from the PLC fault table 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.
%S0013 PRG_CHK Set when background program check is active.
%S0014 PLC_BAT Set to indicate a bad battery in a Release 4 or later CPU. The
contact reference is updated once per sweep.