Siemens Simatic S7 Series System Manual

PLC concepts
4.2 Accessing data
S7-200 SMART
60 System Manual, 09/2015, A5E03822230-AC
4.2
Accessing data
The CPU stores information in different memory locations that have unique addresses. You
can explicitly identify the memory address that you want to access. This allows your program
to have direct access to the information. To access a bit in a memory area, you specify the
address, which includes the memory area identifier, the byte address, and the bit number
(which is also called "byte.bit" addressing).
Table 4- 2 Bit addressing
Elements of a bit address
Description
A
Memory area identifier
B Byte address: byte 3
C
Separator ("byte.bit")
D
Bit location of the byte (bit 4 of 8, bits numbered 7 to 0)
E
Bytes of the memory area
F Bits of the selected byte
In this example, the memory area and byte address ("M3") designates byte 3 of M memory,
with a period (".") to separate the bit address (bit 4).
You can access data in most memory areas (V, I, Q, M, S, L, and SM) as bytes, words, or
double words by using the byte-address format. To access a byte, word, or double word of
data in the memory, you must specify the address in a way similar to specifying the address
for a bit. This includes an area identifier, data size designation, and the starting byte address
of the byte, word, or double-word value, as shown in the following figure.

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.