References; Often-Used Special Memory Bits; E.1 Often-Used Special Memory Bits - Siemens Simatic S7 Series System Manual

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References

The complete list of pre-defined special memory program symbols is available to your

project, in the System Symbol table.

Often-used special memory bits

System symbol name

First_Scan_On

Retentive_Lost

RUN_Power_Up

Overflow_Illegal

Table_Overflow

S7-200 SMART

System Manual, 09/2015, A5E03822230-AC

ON for the first scan cycle only

ON for one scan cycle if retentive data is lost

ON for 1 scan cycle when RUN mode is entered from a power-up condition

Clock pulse that is ON for 30 s, OFF for 30 s, for a cycle time of 1 min.

Clock pulse that is ON for 0.5 s, OFF for 0.5 s, for a cycle time of 1 s.

Scan cycle clock which is ON for one scan cycle and OFF for the next scan cycle

This bit is turned ON for one scan cycle, if the time on the real time clock device

was reset or lost at power-up (resulting in system time lost). This bit can be used

as either an error memory bit, or to invoke a special start-up sequence.

Set to 1 by the execution of certain instructions when the result of the operation

Set to 1 by the execution of certain instructions on overflow or illegal numeric

Set to 1 when a math operation produces a negative result

Set to 1 when an attempt is made to divide by zero

Set to 1 when the Add to Table instruction attempts to overfill the table

Set to 1 when a LIFO or FIFO instruction attempts to read from an empty table

Set to 1 when an attempt is made to convert a non-BCD value to a binary value

Set to 1 when an ASCII value cannot be converted to a valid hexadecimal value

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Simatic s7-200 smart series