Mitsubishi MELSEC-Q Series Programming Manual page 51

1. Floating-point data in a CPU module can be monitored by the monitoring
function of the programming tool.
2. To express 0 in floating-point data, set all of the following bits to 0.
(a) Single-precision floating-point data: b0 to b31
(b) Double-precision floating-point data: b0 to b63
3. The setting range of real number is shown below:
(a) Single-precision floating-point data
128
−2 < Device ≤ −2
(b) Double-precision floating-point data
1023
−2 ≤ Device ≤ −2
4. Do not specify -0 (when only the highest bit of the floating-point real number is
1) for floating-point data. (A floating-point operation with -0 results an operation
error.)
For a CPU module that performs an internal operation of floating-point
operation with double precision, a floating-point operation does not result an
error since -0 is converted to 0 in a CPU module when -0 is specified.
For a CPU module that performs an internal operation of floating-point
operation with single precision, a floating-point operation results an error since
the process speed is given a priority and -0 is used for an operation as it is
when -0 is specified.
(a) The following is the CPU module in which the operation does not result
an error when -0 is specified.
• High Performance model QCPU in which the internal operation is set
to double precision
operation is double precision.)
(b) The following are the CPU modules in which the operation results an
error when -0 is specified.
• Basic model QCPU
• High Performance model QCPU in which the internal operation is set
to single precision
• Universal model QCPU
• LCPU
*1: For operations when an overflow or underflow is occurred or when a special value is input, refer to the User's
Manual (Function Explanation, Program Fundamentals) of the CPU module to be used.
*2: Switching between single precision and double precision of the internal floating-point operation is set in the
PLC system setting of the PLC parameter. For single precision and double precision of floating point
operation, refer to the User's Manual (Function Explanation, Program Fundamentals) of the CPU module to
be used.
*3: The floating point operation is supported with the Basic model QCPU with a serial number whose first five
digits are '04112' or higher.
-126 -126
≤ Device < 2
, 0, 2
-1022 -1022
, 0, −2
*2
(The default setting of internal floating-point
*3
*2
4.4 Method for Specifying Data
4.4.4 Single-precision real/double-precision real data
*1
128
1023
≤ Device ≤ 2
4
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