HD64F2145 datasheet(75/829 Pages) RENESAS

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Rev. 2.0, 08/02, page 35 of 788

2.4.1

General Registers

The H8S/2000 CPU has eight 32-bit general registers. These general registers are all functionally

alike 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 2.7 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).

When the general registers are used as 16-bit registers, the ER registers are divided 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 sixteen 16-bit registers. The E registers (E0 to E7)

are also referred to as extended registers.

When the general registers are used as 8-bit registers, the R registers are divided into 8-bit general

registers designated by the letters RH (R0H to R7H) and RL (R0L to R7L). These registers are

functionally equivalent, providing a maximum sixteen 8-bit registers.

The usage of each register can be selected independently.

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 2.8 shows the

stack.

• 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 2.7 Usage of General Registers

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