Fujitsu MB91260B Series Hardware Manual page 472

/* Use a STB instruction (or LDB instruction, etc.) for 8-bit data access */
STB r4, @r5
The value cannot be guaranteed when accessing it by a different data size in this MB91260B series. For
example, when two consecutive 16-bit data are accessed at a time by using a 32-bit access instruction, the
value of data cannot be guaranteed.
APPENDIX D Notes When Little Endian Area Is Used
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