Siemens Simatic S7 Series System Manual

Program instructions
7.5 Convert
S7-200 SMART
208 System Manual, 09/2015, A5E03822230-AC
7.5.3
Number value to ASCII string conversion
Format of the STRING data type
A string variable is a sequence of characters, with each character stored as a byte. The first
byte of the STRING data type defines the length of the string, which is the number of
character bytes.
The diagram below shows the STRING data type stored as a variable in memory. The string
can have a length of 0 to 254 characters. The maximum storage requirement for a variable
string is 255 bytes (the length byte plus 254 characters).
If a constant string parameter is entered directly in the program editor (126 characters
maximum) or a variable string is initialized in the data block editor (254 characters
maximum), the string assignment must begin and end with double quote characters.
ASCII output number format
● Positive values are written to the output buffer without a sign.
● Negative values are written to the output buffer with a leading minus sign (-).
● Leading zeros to the left of the decimal point (except the digit adjacent to the decimal
point) are suppressed.
● Values are right-justified in the output string.
● Real numbers: Values to the right of the decimal point are rounded to fit in the specified
number of digits to the right of the decimal point.
● Real numbers: The size of the output string must be a minimum of three bytes more than
the number of digits to the right of the decimal point.

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.