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Chapter 9
(2)
Note
300
Data space
The microcontroller device is provided with an address misalign function.
By this function, data of any format (word: 32 bit, halfword: 16 bit, byte: 8 bit)
can be placed to any address in memory, even though the address is not
aligned to the data format (that means address 4n for words, address 2n for
halfwords).
• Unaligned halfword data access
When the LSB of the address is A0 = 1, two byte accesses are performed.
• Unaligned word data access
– When the LSB of the address is A0 = 1, two byte and one halfword
accesses are performed. In total it takes 3 bus cycles.
– When the LSBs of the address are A[1:0] =10
are performed.
Accessing data on misaligned addresses takes more than one bus cycle to
complete data read/write. Consequently, the bus efficiency will drop.
Preliminary User's Manual U18743EE1V2UM00
Bus Control Unit (BCU)
, two halfword accesses
B
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