Comparison Operations - Siemens SIMATIC S5-100U System Manual

STEP 5 Operations

8.1.6 Comparison Operations

Comparison operations compare the contents of the two accumulators. The comparison does not
change the accumulators' contents. Table 8-6 provides an overview of the comparison operations.
An example follows the table.
Table 8-6. Overview of Comparison Operations
Operation Operand
! = F
> < F
> F
> = F
< F
< = F
Processing Comparison Operations
To compare two operands, load them consecutively into the two accumulators. Execution of the
operations is independent of the RLO.
The result is binary and is available as RLO for further program processing. If the comparison is
satisfied, the RLO is "1". Otherwise it is "0".
Executing the comparison operations sets the condition codes (see section 8.4).
Note
When using comparison operations, make sure the operands have the same number
format.
8-30
Compare for "equal to"
The contents of the two accumulators are interpreted as bit patterns
and scanned to see if they are equal.
Compare for "not equal to"
The contents of the two accumulators are interpreted as bit patterns
and compared to see if they are not equal.
Compare for "greater than"
The contents of the two accumulators are interpreted as fixed-point
numbers. They are compared to see if the operand in ACCU 2 is
greater than the operand in ACCU 1.
Compare for "greater than or equal to"
The contents of the two accumulators are interpreted as fixed-point
numbers. They are compared to see if the operand in ACCU 2 is
greater than or equal to the operand in ACCU 1.
Compare for "less than"
The contents of the two accumulators are interpreted as fixed-point
numbers. They are compared to see if the operand in ACCU 2 is
less than the operand in ACCU 1.
Compare for "less than or equal to"
The contents of the two accumulators are interpreted as fixed-point
numbers. They are compared to see if the operand in ACCU 2 is
less than or equal to the operand in ACCU 1.
Meaning
EWA 4NEB 812 6120-02b
S5-100U