Siemens Simatic S7 Series System Manual

Program instructions
7.3 Communication
S7-200 SMART
178 System Manual, 09/2015, A5E03822230-AC
7.3.2
Transmit and receive (Freeport on RS485/RS232)
You can use the Transmit (XMT) and Receive (RCV) instructions for communication
between a S7-200 SMART CPU and other devices through the CPU serial port(s). Each
S7-200 SMART CPU provides an integrated RS485 port (Port 0). The standard CPUs
additionally support an optional CM01 Signal Board (SB) RS232/RS485 port (Port 1). The
communication protocol must be implemented in the user program.
LAD / FBD
STL
Description
XMT TBL, POR
T
The Transmit instruction (XMT) is used in Freeport mode to transmit data by
means of the communications port(s).
RCV TBL, POR
T
The Receive instruction (RCV) initiates or terminates the receive message
function. You must specify a start and an end condition for the Receive box to
operate. Messages received through the specified port (PORT) are stored in
the data buffer (TBL). The first entry in the data buffer specifies the number of
bytes received.

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.