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4.16 Relationship between Data Bus Widths and Control Signals
4.16.1 Bus Access with Big Endians
When external bus access is performed for areas not set by the little endian register
(LER), those areas are handled as big endians.
The FR series usually employs big endians.
■
Data Format
The following shows the relationship between the internal register and external data bus for
each data format.
❍
Word access (during execution of LD and ST instructions)
Figure 4.16-3 Relationship between Internal Register and External Data Bus for Word Access
❍
Half-word access (during execution of LDUH and STH instructions)
Figure 4.16-4 Relationship between Internal Register and External Data Bus for Half-Word Access
AA AA CC
BB BB DD
CC
DD
D31
D31
D07
D15
D23
D23
Internal register External bus
AA
BB
AA
BB
D31
D23
D15
D07
D31
D23
Internal register External bus