Hitachi H8/3692 ユーザーズマニュアル

Rev. 1.0, 07/01, page 11 of 372

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)

General register ER7 has the function of 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 stack pointer and the stack area.