Renesas H8S/2100 Series, Hardware Manual

Page: 58 / 1024

Section 2 CPU
Rev. 1.00 Apr. 28, 2008 Page 32 of 994
REJ09B0452-0100
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 vector table and stack have the same structure as in the H8/300 CPU.
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Address Space
Linear access to a 64-kbyte maximum address space is provided.
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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.
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Instruction Set
All instructions and addressing modes can be used. Only the lower 16 bits of effective
addresses (EA) are valid.
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Exception Vector Table and Memory Indirect Branch Addresses
In normal mode the top area starting at H'0000 is allocated to the exception vector table. One
branch address is stored per 16 bits. The exception vector table structure in normal mode is
shown in figure 2.1. For details of the exception 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 area from H'0000 to
H'00FF. Note that the first part of this range is also used for the exception vector table.
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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.