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Section 2 CPU
General
Data Type
Register
Word data
Rn
Word data
En
Longword data
ERn
Legend
ERn:
General register
En:
General register E
Rn:
General register R
MSB:
Most significant bit
LSB:
Least significant bit
2.5.2
Memory Data Formats
Figure 2.8 shows the data formats on memory. The H8/300H CPU can access word data and
longword data on memory, but word or longword data must begin at an even address. If an attempt
is made to access word or longword data at an odd address, no address error occurs but the least
significant bit of the address is regarded as 0, so the access starts at the preceding address. This
also applies to instruction fetches.
Rev. 4.00 Jan 26, 2006 page 32 of 938
REJ09B0276-0400
Data Format
15
MSB
31
MSB
Figure 2.7 General Register Data Formats
15
MSB
0
LSB
16
15
0
LSB
0
LSB
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