Siemens Simatic S7 Series System Manual

PLC concepts
4.2 Accessing data
S7-200 SMART
70 System Manual, 09/2015, A5E03822230-AC
The following table provides an example of the fixed mapping convention (established by
STEP 7 Micro/WIN SMART and downloaded as part of the I/O configuration, in the system
block).
Table 4- 18 CPU mapping convention
CPU
Signal
board
Expansion
module 0
Expansion
module 1
Expansion
module 2
Expansion
module 3
Expansion
module 4
Expansion
module 5
Starting
address
I0.0
Q0.0
I7.0
Q7.0
AI12
AQ12
I8.0
Q8.0
AI16
AQ16
I12.0
Q12.0
AI32
AQ32
I16.0
Q16.0
AI48
AQ48
I20.0
Q20.0
AI64
AQ64
I24.0
Q24.0
AI80
AQ80
I28.0
Q28.0
AI96
AQ96
4.2.6
Using pointers for indirect addressing
Indirect addressing uses a pointer to access data in memory. Pointers are double word
memory locations that contain the address of another memory location. You can only use
V memory locations, L memory locations, or accumulator registers (AC1, AC2, AC3) as
pointers. To create a pointer, you must use the Move Double Word instruction to move the
address of the indirectly addressed memory location to the pointer location. Pointers can
also be passed to a subroutine as a parameter.
An S7-200 SMART CPU allows pointers to access the following memory areas: I, Q, V, M, S,
AI, AQ, SM, T (current value only), and C (current value only). You cannot use indirect
addressing to access an individual bit or to access HC, L or accumulator memory areas.
To indirectly access the data in a memory address, you create a pointer to that location by
entering an ampersand character (&) and the first byte of the memory location to be
addressed. The input operand of the instruction must be preceded with an ampersand (&) to
signify that the address of a memory location, instead of its contents, is to be moved into the
location identified in the output operand of the instruction (the pointer).

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.