32C87 datasheet(24/91 Pages) RENESAS

24 / 91 page

M32C/87 Group (M32C/87, M32C/87A, M32C/87B)

2. Central Processing Unit (CPU)

REJ03B0127-0151 Rev.1.51 Jul 31, 2008

Page 24 of 85

2.1

General Registers

2.1.1

Data Registers (R0, R1, R2, and R3)

R0, R1, R2, and R3 are 16-bit registers for transfer, arithmetic and logic operations. R0 and R1 can be split into

high-order (R0H/R1H) and low-order bits (R0L/R1L) to be used separately as 8-bit data registers.

R0 can be combined with R2 and used as a 32-bit data register (R2R0). The same applies to R3R1.

2.1.2

Address Registers (A0 and A1)

A0 and A1 are 24-bit registers used for A0-/A1-indirect addressing, A0-/A1-relative addressing, transfer,

arithmetic and logic operations.

2.1.3

Static Base Register (SB)

SB is a 24-bit register used for SB-relative addressing.

2.1.4

Frame Base Register (FB)

FB is a 24-bit register used for FB-relative addressing.

2.1.5

User Stack Pointer (USP) and Interrupt Stack Pointer (ISP)

The stack pointers (SP), USP and ISP, are 24 bits wide each. The U flag is used to switch between USP and ISP.

Refer to 2.1.8 Flag Register (FLG) for details on the U flag. Set USP and ISP to even addresses to execute an

interrupt sequence efficiently.

2.1.6

Interrupt Table Register (INTB)

INTB is a 24-bit register indicating the starting address of a relocatable interrupt vector table.

2.1.7

Program Counter (PC)

PC is 24 bits wide and indicates the address of the next instruction to be executed.

2.1.8

Flag Register (FLG)

FLG is a 16-bit register indicating the CPU state.

2.1.8.1

Carry Flag (C)

The C flag indicates whether or not carry or borrow has been generated after executing an instruction.

2.1.8.2

Debug Flag (D)

The D flag is for debugging only. Set it to 0.

2.1.8.3

Zero Flag (Z)

The Z flag becomes 1 when an arithmetic operation results in 0; otherwise becomes 0.

2.1.8.4

Sign Flag (S)

The S flag becomes 1 when an arithmetic operation results in a negative value; otherwise becomes 0.

2.1.8.5

2.1.8.6

Overflow Flag (O)

The O flag becomes 1 when an arithmetic operation results in an overflow; otherwise becomes 0.

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