Siemens Simatic S7 Series System Manual

S7-200 SMART
System Manual, 09/2015, A5E03822230-AC
693
References
E
E.1
Often-used special memory bits
The complete list of pre-defined special memory program symbols is available to your
project, in the System Symbol table.
Table E- 1 Often-used special memory bits
SM address
System symbol name
Description
SM0.0
Always_On
Always ON
SM0.1
First_Scan_On
ON for the first scan cycle only
SM0.2 Retentive_Lost ON for one scan cycle if retentive data is lost
SM0.3
RUN_Power_Up
ON for 1 scan cycle when RUN mode is entered from a power-up condition
SM0.4 Clock_60s Clock pulse that is ON for 30 s, OFF for 30 s, for a cycle time of 1 min.
SM0.5
Clock_1s
Clock pulse that is ON for 0.5 s, OFF for 0.5 s, for a cycle time of 1 s.
SM0.6
Clock_Scan
Scan cycle clock which is ON for one scan cycle and OFF for the next scan cycle
SM0.7 RTC_Lost 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.
SM1.0 Result_0 Set to 1 by the execution of certain instructions when the result of the operation
= 0
SM1.1 Overflow_Illegal Set to 1 by the execution of certain instructions on overflow or illegal numeric
value
SM1.2
Neg_Result
Set to 1 when a math operation produces a negative result
SM1.3
Divide_By_0
Set to 1 when an attempt is made to divide by zero
SM1.4
Table_Overflow
Set to 1 when the Add to Table instruction attempts to overfill the table
SM1.5
Table_Empty
Set to 1 when a LIFO or FIFO instruction attempts to read from an empty table
SM1.6
Not_BCD
Set to 1 when an attempt is made to convert a non-BCD value to a binary value
SM1.7
Not_Hex
Set to 1 when an ASCII value cannot be converted to a valid hexadecimal value

Siemens Simatic S7 Series Specifications

General

CPU	Varies by model (e.g., S7-300, S7-400, S7-1200, S7-1500)
Communication Interfaces	PROFIBUS, PROFINET, Ethernet, MPI
Programming	TIA Portal, STEP 7
Programming Languages	LAD, FBD, STL, SCL, GRAPH
I/O Modules	Digital, Analog, Specialty modules available
Operating Temperature	0°C to 60°C (standard models)
Mounting	DIN rail mounting
Operating Voltage	24V DC or 120/230V AC (varies by model)
Protection Class	IP20 (standard models)
Memory	Varies depending on the S7 model. Includes work memory (RAM) for program execution, load memory (EEPROM or Flash) for program storage, and system memory for operating system functions. Memory sizes range from kilobytes to megabytes.