Condition Code Generation - Siemens S5-100U User Manual

S5-100U
8.4

Condition Code Generation

The processor of the programmable controller has the following three condition codes:
• CC 0
• CC 1
• OV (overflow)
The following operations affect the condition codes.
• Comparison operations
• Arithmetic operations
• Shift operations
• Some conversion operations
The state of the condition codes represents a condition for the various jump operations.
Condition Code Generation for Comparison Operations
Execution of comparison operations sets condition codes CC 0 and CC 1 (see Table 8-31). The
overflow condition code is not affected. Comparison operations do affect the RLO. When a
comparison is satisfied, the RLO is 1. This allows you to use the "JC" conditional jump operation
after a comparison operation.
Table 8-31. Condition Code Settings for Comparison Operations
Contents of ACCU 2 as
Compared to Contents
of ACCU 1
Equal to
Less than
Greater than
Condition Code Generation for Arithmetic Operations
Execution of arithmetic operations sets all condition codes according to the result of the arithmetic
operation (see Table 8-32).
Table 8-32. Condition Code Settings for Fixed-Point Arithmetic Operations
Result after
Arithmetic Operation
is Executed
< - 32768
- 32768 to - 1
0
+1 to +32767
> +32767
(-) 65536*
*
This number is the result of the calculation -32768 - 32768
EWA 4NEB 812 6120-02
Condition Codes
CC 1 CC 0
0 0
0 1
1 0
Condition Codes
CC 1 CC 0
1 0
0 1
0 0
1 0
0 1
0 0
STEP 5 Operations
Possible
Jump Operations
OV
JZ
JN, JM
JN, JP
Possible
Jump Operations
OV
1 JN, JP, JO
0 JN, JM
0 JZ
0 JN, JP
1 JN, JM, JO
1 JZ, JO
8-69