Big Endian Method Usage Restrictions In Nec Development Tools - NEC V850E/MA1 User Manual

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4.5.4 Big endian method usage restrictions in NEC development tools

(1) When using a debugger (ID850)
The big endian method is supported only in the memory window display.
(2) When using a compiler (CA850)
(a) Restrictions in C language
(i) There are restrictions for variables allocated to/located in the big endian space, as shown below.
• union cannot be used.
• bitfield cannot be used.
• Access with cast (changing access size) cannot be used.
• Variables with initial values cannot be used.
(ii) It is necessary to specify the following optimization inhibit options because optimization may cause a
change in the access size.
• For global optimization part (opt850)... -Wo, -XTb
• For optimization depending on model part (impr850)... -Wi, +arg_reg_opt=OFF, +stld_trans_opt=OFF
The specification of the optimization inhibit options shown above is not necessary, however, if the
access is not an access with cast or with masking/shifting
Note This is on the condition that a pattern that may cause the following optimization is not used.
However, because it is very difficult for users to check the patterns completely in cases such
as when several patterns are mixed (especially for optimization depending on model part), it
is recommended that the optimization inhibit options shown above be specified.
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CHAPTER 4 BUS CONTROL FUNCTION
Figure 4-2. Big Endian Addresses Within Word
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Figure 4-3. Little Endian Addresses Within Word
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