Description of System Bits %S0 to %S7
Original instructions
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Detailed Description
Description of system bits %S0 to %S7:
Bit
Symbol
%S0
COLDSTART
Function
Cold start
Initial State
1 (1 cycle)
Platforms
M340: Yes M580: Yes M580 Safety: Yes Quantum: Yes Momentum: Yes Premium: Yes Atrium: Yes
Normally on 0, this bit is set on 1 by:
  • power restoral with loss of data (battery fault found)
  • the user program
  • the terminal
  • a change of cartridge (PCMCIA on Premium and Quantum)
This bit is set to 1 during the first complete restored cycle of the PLC either in RUN or in STOP mode. It is reset to 0 by the system before the following cycle.
To detect the first cycle in run after cold start, refer to %SW10.
Safety restrictions: M580 Safety: %S0 bit can be used only in process tasks and has no influence on SAFE task.
%S0 is not always set in the first scan of the PLC. If a signal set for every start of the PLC is needed, %S21 should be used instead.
For details on operating modes refer to:
%S1
WARMSTART
Function
Warm restart
Initial State
0
Platforms
M340: Yes M580: Yes M580 Safety: Yes Quantum: Yes Momentum: Yes Premium: Yes Atrium: Yes
Normally at 0, this bit is set to 1 by:
  • power is restored with data save,
  • the user program,
  • the terminal,
It is reset to 0 by the system at the end of the first complete cycle and before the outputs are updated.
%S1 is not always set in the first scan of the PLC. If a signal set for every start of the PLC is needed, %S21 should be used instead.
%S4
TB10MS
Function
Timebase 10 ms
Initial State
–
Platforms
M340: Yes M580: Yes M580 Safety: Yes Quantum: Yes Momentum: Yes Premium: Yes Atrium: Yes
An internal timer regulates the change in status of this bit.
It is asynchronous in relation to the PLC cycle.
Graph:
%S5
TB100MS
Function
Timebase 100 ms
Initial State
–
Platforms
M340: Yes M580: Yes M580 Safety: Yes Quantum: Yes Momentum: Yes Premium: Yes Atrium: Yes
Same as %S4
%S6
TB1SEC
Function
Time base 1 s
Initial State
–
Platforms
M340: Yes M580: Yes M580 Safety: Yes Quantum: Yes Momentum: Yes Premium: Yes Atrium: Yes
Same as %S4
%S7
TB1MIN
Function
Time base 1 min
Initial State
–
Platforms
M340: Yes M580: Yes M580 Safety: Yes Quantum: Yes Momentum: Yes Premium: Yes Atrium: Yes
Same as %S4