R5F72115D160FPV datasheet(116/1228 Pages) RENESAS

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Section 5 Exception Handling

Rev. 2.00 May. 08, 2008 Page 92 of 1200

REJ09B0344-0200

5.5.3

Interrupt Exception Handling

When an interrupt occurs, its priority level is ascertained by the interrupt controller (INTC). NMI

is always accepted, but other interrupts are only accepted if they have a priority level higher than

the priority level set in the interrupt mask level bits (I3 to I0) of the status register (SR).

When an interrupt is accepted, interrupt exception handling begins. In interrupt exception

handling, the CPU fetches the exception service routine start address which corresponds to the

accepted interrupt from the exception handling vector table, and saves SR and the program counter

(PC) to the stack. In the case of interrupt exception handling other than NMI or UBC with usage

of the register banks enabled, general registers R0 to R14, control register GBR, system registers

MACH, MACL, and PR, and the vector number of the interrupt exception handling to be executed

are saved in the register banks. In the case of exception handling due to an address error, NMI

interrupt, UBC interrupt, or instruction, saving is not performed to the register banks. If saving has

been performed to all register banks (0 to 14), automatic saving to the stack is performed instead

of register bank saving. In this case, an interrupt controller setting must have been made so that

setting to accept register bank overflow exceptions has been made (the BOVE bit in IBNR of the

INTC is 1), register bank overflow exception occurs. Next, the priority level value of the accepted

interrupt is written to the I3 to I0 bits in SR. For NMI, however, the priority level is 16, but the

value set in the I3 to I0 bits is H'F (level 15). Then, after jumping to the start address fetched from

the exception handling vector table, program execution starts. The jump that occurs is not a

delayed branch. See section 6.6, Operation, for further details of interrupt exception handling.

R5F72115D160FPV Datasheet(PDF) 116 Page - Renesas Technology Corp