RX230 Datasheet, PDF (36/177 Pages) Renesas Technology Corp – 54-MHz 32-bit RX MCUs, built-in FPU, 88.56 DMIPS, up to 512-KB flash memory

RX230 Group, RX231 Group
2. CPU
2.1 General-Purpose Registers (R0 to R15)
This CPU has sixteen 32-bit general-purpose registers (R0 to R15). R0 to R15 can be used as data registers or address
registers.
R0, a general-purpose register, also functions as the stack pointer (SP).
The stack pointer is switched to operate as the interrupt stack pointer (ISP) or user stack pointer (USP) by the value of the
stack pointer select bit (U) in the processor status word (PSW).
2.2 Control Registers
(1) Interrupt stack pointer (ISP) and user stack pointer (USP)
The stack pointer (SP) can be either of two types, the interrupt stack pointer (ISP) or the user stack pointer (USP).
Whether the stack pointer operates as the ISP or USP depends on the value of the stack pointer select bit (U) in the
processor status word (PSW).
Set the ISP or USP to a multiple of 4 to reduce the number of cycles required to execute interrupt sequences and
instructions entailing stack manipulation.
(2) Exception table register (EXTB)
The exception table register (EXTB) specifies the address where the exception vector table starts.
Set the EXTB to a multiple of 4 to reduce the number of cycles required to execute interrupt sequences and instructions
entailing stack manipulation.
(3) Interrupt table register (INTB)
The interrupt table register (INTB) specifies the address where the interrupt vector table starts.
Set the INTB to a multiple of 4 to reduce the number of cycles required to execute interrupt sequences and instructions
entailing stack manipulation.
(4) Program counter (PC)
The program counter (PC) indicates the address of the instruction being executed.
(5) Processor status word (PSW)
The processor status word (PSW) indicates the results of instruction execution or the state of the CPU.
(6) Backup PC (BPC)
The backup PC (BPC) is provided to speed up response to interrupts.
After a fast interrupt has been generated, the contents of the program counter (PC) are saved in the BPC register.
(7) Backup PSW (BPSW)
The backup PSW (BPSW) is provided to speed up response to interrupts.
After a fast interrupt has been generated, the contents of the processor status word (PSW) are saved in the BPSW. The
allocation of bits in the BPSW corresponds to that in the PSW.
(8) Fast interrupt vector register (FINTV)
The fast interrupt vector register (FINTV) is provided to speed up response to interrupts.
The FINTV register specifies a branch destination address when a fast interrupt has been generated.
R01DS0261EJ0110 Rev.1.10
Oct 30, 2015
Page 36 of 177