Big Endian Bus Access - Fujitsu FR60 Hardware Manual

32-bit microcontroller mb91301 series

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CHAPTER 4 EXTERNAL BUS INTERFACE

Big Endian Bus Access

With the exception of the CS0 area of the FR family, either the big endian method or

the little endian method can be selected for each chip select area. If "0" is set for the

LEND bit of the ACR register, the area is treated as big endian. The FR family is

normally big endian and performs external bus access.

■ Data Format

The relationship between the internal register and the external data bus is as follows:

❍ Word access (when LD/ST instruction executed)

Figure 4.4-4 Relationship between Internal Register and External Data Bus for Word Access

❍ Halfword access (LDUH/STH instruction executed)

Figure 4.4-5 Relationship between the Internal Register and External Data Bus for Halfword Access

Internal register

a) Output address low-order

Internal register External bus

External register

b) Output address low-order

Internal register External bus