SH7201 Datasheet, PDF (94/1196 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7200 Series

Section 3 Floating-Point Unit (FPU)
31 30
23 22
0
x
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Nxxxxxxxxxxxxxxxxxxxxxx
N = 1: sNaN
N = 0: qNaN
Figure 3.3 Single-Precision NaN Bit Pattern
An sNaN is input in an operation, except copy, FABS, and FNEG, that generates a floating-point
value.
• When the EN.V bit in FPSCR is 0, the operation result (output) is a qNaN.
• When the EN.V bit in FPSCR is 1, an invalid operation exception will be generated. In this
case, the contents of the operation destination register are unchanged.
If a qNaN is input in an operation that generates a floating-point value, and an sNaN has not been
input in that operation, the output will always be a qNaN irrespective of the setting of the EN.V bit
in FPSCR. An exception will not be generated in this case.
The qNAN values as operation results are as follows:
• Single-precision qNaN: H'7FBF FFFF
• Double-precision qNaN: H'7FF7 FFFF FFFF FFFF
See the individual instruction descriptions for details of floating-point operations when a non-
number (NaN) is input.
3.2.3 Denormalized Numbers
For a denormalized number floating-point value, the exponent field is expressed as 0, and the
fraction field as a non-zero value.
In the SH2A-FPU, the DN bit in the status register FPSCR is always set to 1, therefore a
denormalized number (source operand or operation result) is always flushed to 0 in a floating-
point operation that generates a value (an operation other than copy, FNEG, or FABS).
When the DN bit in FPSCR is 0, a denormalized number (source operand or operation result) is
processed as it is. See the individual instruction descriptions for details of floating-point
operations when a denormalized number is input.
Rev. 2.00 Sep. 07, 2007 Page 66 of 1164
REJ09B0321-0200