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2.2
CPU Operating Modes
The H8S/2600 CPU has two operating modes: normal and advanced. Normal mode supports a
maximum 64-kbyte address space. Advanced mode supports a maximum 16-Mbyte total address
space. The mode is selected by the mode pins.
2.2.1
Normal Mode
The exception-handling vector table and stack have the same structure as in the H8/300 CPU.
• Address Space
The H8S/2600 CPU provides linear access to a maximum 64-kbyte address space.
• 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 is referenced in the
register indirect addressing mode with pre-decrement (@–Rn) or post-increment (@Rn+) and a
carry or borrow occurs, however, the value in the corresponding extended register (En) will be
affected.
• Instruction Set
All instructions and addressing modes can be used. Only the lower 16 bits of effective
addresses (EA) are valid.
• Exception-handling Vector Table and Memory Indirect Branch Addresses
In normal mode the top area starting at H'0000 is allocated to the exception-handling vector
table. One branch address is stored per 16 bits. The exception-handling vector table in normal
mode is shown in figure 2.1. For details of the exception-handling vector table, see section 4,
Exception Handling.
The memory indirect addressing mode (@@aa:8) employed in the JMP and JSR instructions
uses an 8-bit absolute address included in the instruction code to specify a memory operand
that contains a branch address. In normal mode the operand is a 16-bit word operand,
providing a 16-bit branch address. Branch addresses can be stored in the top area from H'0000
to H'00FF. Note that this area is also used for the exception-handling vector table.
• Stack Structure
When the program counter (PC) is pushed onto the stack in a subroutine call, and the PC,
condition-code register (CCR), and extended control register (EXR) are pushed onto the stack
in exception handling, they are stored as shown in figure 2.2. EXR is not pushed onto the
stack in interrupt control mode 0. For details, see section 4, Exception Handling.
Note: Normal mode is not available in this LSI.
Rev. 1.00, 09/03, page 18 of 704
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