Siemens Simatic S7 Series System Manual

Program instructions
7.18 Subroutine
S7-200 SMART
350 System Manual, 09/2015, A5E03822230-AC
There are no automatic data type conversions performed on the input or output parameters.
For example, if the variable table specifies that a parameter has the data type REAL, and in
the calling routine a double word (DWORD) is specified for that parameter, the value in the
subroutine will be a double word.
When values are passed to a subroutine, they are placed into the local memory of the
subroutine. The left-most column of the variable table shows the local memory address for
each passed parameter. Input parameter values are copied to the subroutine's local memory
when the subroutine is called. Output parameter values are copied from the subroutine's
local memory to the specified output parameter addresses when the subroutine execution is
complete.
The data element size and type are represented in the coding of the parameters.
Assignment of parameter values to local memory in the subroutine is as follows:
● Parameter values are assigned to local memory in the order specified by the call
subroutine instruction with parameters starting at L 0.0.
● One to eight consecutive bit parameter values are assigned to a single byte starting with
Lx.0 and continuing to Lx.7.
● Byte, word, and double word values are assigned to local memory on byte boundaries
(LBx, LWx, or LDx).
In the Call Subroutine instruction with parameters, parameters must be arranged in order
with input parameters first, followed by input/output parameters, and then followed by output
parameters.
If you are programming in STL, the format of the CALL instruction is:
CALL subroutine number, parameter 1, parameter 2, ... , parameter 16
Example: Subroutine and return from subroutine instructions
LAD
STL
MAIN
On the first scan, call subroutine 0
for initialization.
Network 1
LD SM0.1
CALL SBR_0
SBR0
You can use a conditional return to
leave the subroutine before the last
network.
Network 1
LD M14.3
CRET
SBR0
This network will be skipped if
M14.3 is ON.
Network 2
LD SM0.0
MOVB 10, VB0

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.