H8S2245 datasheet(71/818 Pages) RENESAS

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Section 2 CPU

Rev.3.00 Mar. 26, 2007 Page 29 of 772

REJ09B0355-0300

2.4.2

General Registers

The 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

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 sixteen 16-bit

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

The R registers divide 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.

Figure 2.8 illustrates the usage of the general 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 2.8 Usage of General Registers

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 2.9 shows the

stack.

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