Appendix 3.4.2 Error Check Processing For Floating-Point Data Comparison Instructions - Mitsubishi Electric melsec q00ujcpu User Manual

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
special values are input, the CPU module detects "OPERATION ERROR" (error code: 4140).
When the LDE , ANDE , ORE , LDED , ANDED , and/or ORED
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.
• 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.
Example 1) Detecting "OPERATION ERROR" (error code: 4140) in the LDE
[Ladder 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.
APPENDICES
) is checked, and if those
instructions ( indicates one of the fol-
instruction
[List mode]
App - 48
1
2
3
APPEN-
DIX
6
7
8