Renesas M32R-FPU Manual Do Utilizador

APPENDICES

APPENDICES-29

M32R-FPU Software Manual (Rev.1.01)

Appendix 7 Precautions

Appendix 7.1 Precautions to be taken when aligning data

When aligning or allocating the data area following the code area in a program, the

alignment must be done from an address that has an adjusted word alignment.

If the data area is aligned or allocated without adjusting the word alignment, a 16-bit

instruction may exist in the high-order halfword of the word, and data with MSB of “1”

may be aligned to the following halfword.  In this case, the M32R family upward-

compatible CPU recognizes the 16-bit instruction and the data as a pair of parallel

executable instructions and executes the instructions as such.

In consideration of the upward compatibility of software when programming, if the high-

order halfword has a 16-bit instruction, make sure that the following data area is aligned

or allocated from an address that has an adjusted word alignment.

MSB

MSB

16-bit instruction

data

0

1

+0

+1

+2

+3

1 word

data

APPENDIX 7

Appendix 7 Precautions