H838532H datasheet(44/508 Pages) RENESAS

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Section 2 CPU

Rev. 1.00 May 30, 2008 Page 24 of 484

REJ09B0436-0100

2.2.1

General Registers

The H8/300H CPU has eight 32-bit general registers. These general registers are all functionally

identical and can be used as both address registers and data registers. When a general register is

used as a data register, it can be accessed as a 32-bit, 16-bit, or 8-bit register. Figure 2.3 illustrates

the usage of the general registers. When the general registers are used as 32-bit registers or address

registers, they are designated by the letters ER (ER0 to ER7).

The ER registers divide into 16-bit general registers designated by the letters E (E0 to E7) and R

(R0 to R7). These registers are functionally equivalent, providing a maximum of sixteen 16-bit

registers. The E registers (E0 to E7) are also referred to as extended registers.

The R registers divide into 8-bit registers designated by the letters RH (R0H to R7H) and RL (R0L

to R7L). These registers are functionally equivalent, providing a maximum of sixteen 8-bit

registers.

The usage of each register can be selected independently.

• Address registers

• 32-bit registers

• 16-bit registers

• 8-bit registers

ER registers

(ER0 to ER7)

E registers (extended registers)

(E0 to E7)

R registers

(R0 to R7)

RH registers

(R0H to R7H)

RL registers

(R0L to R7L)

Figure 2.3 Usage of General Registers

General register ER7 has the function of the stack pointer (SP) in addition to its general-register

function, and is used implicitly in exception handling and subroutine calls. Figure 2.4 shows the

relationship between the stack pointer and the stack area.

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