R32C/118 Group
2. Central Processing Unit (CPU)
2.1
2.1.1
General Purpose Registers
Data Registers (R2R0, R3R1, R6R4, and R7R5)
These 32-bit registers are primarily used for transfers and arithmetic/logic operations.
Each of the registers can be divided into upper and lower 16-bit registers, e.g. R2R0 can be divided into
R2 and R0, R3R0 can be divided into R3 and R1, etc.
Moreover, data registers R2R0 and R3R1 can be divided into four 8-bit data registers: upper (R2H and
R3H), mid-upper (R2L and R3L), mid-lower (R0H and R1H), and lower (R0L and R1L).
2.1.2
Address Registers (A0, A1, A2, and A3)
These 32-bit registers have functions similar to data registers. They are also used for address register
indirect addressing and address register relative addressing.
2.1.3
Static Base Register (SB)
This 32-bit register is used for SB relative addressing.
2.1.4
Frame Base Register (FB)
This 32-bit register is used for FB relative addressing.
2.1.5
Program Counter (PC)
This 32-bit counter indicates the address of the instruction to be executed next.
2.1.6
Interrupt Vector Table Base Register (INTB)
This 32-bit register indicates the start address of a relocatable vector table.
2.1.7
User Stack Pointer (USP) and Interrupt Stack Pointer (ISP)
Two types of 32-bit stack pointers (SPs) are provided: user stack pointer (USP) and interrupt stack
pointer (ISP).
Use the stack pointer select flag (U flag) to select either the user stack pointer (USP) or the interrupt
stack pointer (ISP). The U flag is bit 7 in the flag register (FLG). Refer to 2.1.8 “Flag Register (FLG)” for
details.
To minimize the overhead of interrupt sequence due to less memory access, set the user stack pointer
(USP) or the interrupt stack pointer (ISP) to a multiple of 4.
2.1.8
Flag Register (FLG)
This 32-bit register indicates the CPU status.
2.1.8.1
Carry Flag (C flag)
This flag becomes 1 when any of the carry, borrow, shifted-out bit, etc. is generated in the arithmetic
logic unit (ALU).
2.1.8.2
Debug Flag (D flag)
This flag is only for debugging. Only set this bit to 0.
2.1.8.3
Zero Flag (Z flag)
This flag becomes 1 when the result of an operation is 0; otherwise it is 0.
2.1.8.4
Sign Flag (S flag)
This flag becomes 1 when the result of an operation is a negative value; otherwise it is 0.
REJ03B0255-0100 Rev.1.00 Nov 19, 2009
Page 24 of 122
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