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Appendix 3.4.2 Error check processing for floating-point data comparison
instructions
(1) Input data check
Error check processing for floating-point data comparison instructions performed in the Universal model QCPU
are enhanced. Input of a "special value" (-0, nonnumeric, unnormalized number, or
) is checked, and if those
special values are input, the CPU module detects “OPERATION ERROR” (error code: 4140).
When the LDE , ANDE , ORE , LDED , ANDED , and/or ORED instructions ( indicates one of the fol-
lowings; =,<>,<,>,<=,>=) are used in the program, “OPERATION ERROR” (error code: 4140) may be detected if
invalid floating-point data exist. This occurs even when interlocks are provided using the valid data flags (the sig-
nal which shows the floating-point validity).
Invalid floating-point data are not stored in the result of operations performed in the Universal model QCPU.
Those invalid data are considered to be stored in the following cases:
lowings; =,<>,<,>,<=,>=) are used in the program, “OPERATION ERROR” (error code: 4140) may be detected if
invalid floating-point data exist. This occurs even when interlocks are provided using the valid data flags (the sig-
nal which shows the floating-point validity).
Invalid floating-point data are not stored in the result of operations performed in the Universal model QCPU.
Those invalid data are considered to be stored in the following cases:
• The same device is used for storing floating-point data and other data, such as binary values, BCD values,
and strings.
Use different devices for storing floating-point data and data other than floating-point data.
Use different devices for storing floating-point data and data other than floating-point data.
• Floating-point data externally written are invalid.
Take measures on the external-source side so that valid data are written.
If an error occurs in the floating-point data comparison instructions, take appropriate measures to
remove error causes described above.
remove error causes described above.
[Ladder mode]
[List mode]
In the ladder block starting from the step 104, the floating-point data comparison instructions of the step 105 and
109 are not executed when the M101 (valid data flag) is off.
However, the LDE<= instruction of the step 105 and the ORE>= instruction of the step 109 are executed regard-
less of the execution result of the LD instruction of the step 104 in the program above.
Therefore, even when the M101 is off, “OPERATION ERROR” (error code: 4140) will be detected in the LDE<=
instruction of the step 105 if a "special value" is stored in D100.
For the method of avoiding “OPERATION ERROR”, refer to(2) in this section.
109 are not executed when the M101 (valid data flag) is off.
However, the LDE<= instruction of the step 105 and the ORE>= instruction of the step 109 are executed regard-
less of the execution result of the LD instruction of the step 104 in the program above.
Therefore, even when the M101 is off, “OPERATION ERROR” (error code: 4140) will be detected in the LDE<=
instruction of the step 105 if a "special value" is stored in D100.
For the method of avoiding “OPERATION ERROR”, refer to(2) in this section.
Example 1) Detecting “OPERATION ERROR” (error code: 4140) in the LDE instruction