HD6433644R datasheet(38/549 Pages) RENESAS

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Section 2 CPU

Rev. 6.00 Sep 12, 2006 page 18 of 526

REJ09B0326-0600

2.2

2.2.1

General Registers

All the general registers can be used as both data registers and address registers.

When used as data registers, they can be accessed as 16-bit registers (R0 to R7), or the high bytes

(R0H to R7H) and low bytes (R0L to R7L) can be accessed separately as 8-bit registers.

When used as address registers, the general registers are accessed as 16-bit registers (R0 to R7).

R7 also functions as the stack pointer (SP), used implicitly by hardware in exception processing

and subroutine calls. When it functions as the stack pointer, as indicated in figure 2.2, SP (R7)

points to the top of the stack.

Lower address side [H'0000]

Upper address side [H'FFFF]

Unused area

Stack area

SP (R7)

Figure 2.2 Stack Pointer

2.2.2

Control Registers

The CPU control registers include a 16-bit program counter (PC) and an 8-bit condition code

Program Counter (PC): This 16-bit register indicates the address of the next instruction the CPU

will execute. All instructions are fetched 16 bits (1 word) at a time, so the least significant bit of

the PC is ignored (always regarded as 0).

HD6433644R Datasheet(PDF) 38 Page - Renesas Technology Corp