RX64M_15 Datasheet, PDF (66/230 Pages) Renesas Technology Corp – Renesas MCUs

RX64M 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) / 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).
(2) Exception Table Register (EXTB)
The exception table register (EXTB) specifies the address where the exception vector table starts.
(3) Interrupt Table Register (INTB)
The interrupt table register (INTB) specifies the address where the interrupt vector table starts.
(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.
(9) Floating-Point Status Word (FPSW)
The floating-point status word (FPSW) indicates the results of floating-point operations.
When an exception handling enable bit (Ej) enables the exception handling (Ej = 1), the exception cause can be identified
by checking the corresponding Cj flag in the exception handling routine. If the exception handling is masked (Ej = 0), the
occurrence of exception can be checked by reading the Fj flag at the end of a series of processing. Once the Fj flag has
been set to 1, this value is retained until it is cleared to 0 by software (j = X, U, Z, O, or V).
R01DS0173EJ0100 Rev.1.00
Jul 31, 2014
Page 66 of 230