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2.2
CPU Operating Modes
The H8SX CPU has four operating modes: normal, middle, advanced, and maximum modes. As
for selecting the mode, see section 3.1, Operating Mode Selection.
CPU operating modes
2.2.1
Normal Mode
In normal mode, the exception handling vector table and stack have the same structure as in the
H8/300 CPU.
Note
This LSI does not support this mode.
• Address Space
A maximum address space of 64 kbytes can be accessed.
• Extended Registers (En)
The extended registers (E0 to E7) can be used as 16-bit registers, or as the upper 16-bit
segments of 32-bit registers. When En is used as a 16-bit register it can contain any value, even
when the corresponding general register (Rn) is used as an address register. If the general
register Rn is referenced in the register indirect addressing mode with pre-/post-increment or
decrement and a carry or borrow occurs, however, the value in the corresponding extended
register will be affected.
• Instruction Set
All instructions and addressing modes can be used. Only the lower 16 bits of effective
addresses (EA) are valid.
Normal mode
Middle mode
Advanced mode
Maximum mode
Figure 2.1 CPU Operating Modes
Maximum 64 Kbytes for program
and data areas combined
Maximum 16-Mbyte program
area and 64-Kbyte data area,
maximum 16 Mbytes for program
and data areas combined
Maximum 16-Mbyte program
area and 4-Gbyte data area,
maximum 4 Gbytes for program
and data areas combined
Maximum 4 Gbytes for program
and data areas combined
Rev.2.00 Jun. 28, 2007 Page 17 of 666
REJ09B0311-0200
Section 2 CPU
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