Siemens Simatic S7 Series System Manual

Program instructions
7.4 Compare
S7-200 SMART
System Manual, 09/2015, A5E03822230-AC
193
LAD contacts, FBD boxes
STL
Comparison result
LDB= IN1, IN2
OB= IN1, IN2
AB= IN1, IN2
Compare two unsigned byte values:
The result is TRUE, if IN1 = IN2
LDW= IN1, IN2
OW= IN1, IN2
AW= IN1, IN2
Compare two signed integer values:
The result is TRUE, if IN1 = IN2
LDD= IN1, IN2
OD= IN1, IN2
AD= IN1, IN2
Compare two signed double integer values:
The result is TRUE, if IN1 = IN2
LDR= IN1, IN2
OR= IN1, IN2
AR= IN1, IN2
Compare two signed real values:
The result is TRUE, if IN1 = IN2
Note
The following conditions cause a non-fatal error, set power flow to OFF (ENO bit = 0), and
use value 0 as the result of the comparison
•
Illegal indirect address is encountered (any compare instruction)
•
Illegal real number (for example, NaN) is encountered for compare real instruction
To prevent these conditions from occurring, ensur
e that you properly initialize pointers and
values that contain real numbers before executing compare instructions that use these
values.
Compare instructions are executed regardless of the state of power flow
.

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.