H838532H datasheet(95/508 Pages) RENESAS

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Section 3 Exception Handling

Rev. 1.00 May 30, 2008 Page 75 of 484

REJ09B0436-0100

Interrupt operation is described as follows.

• When an interrupt condition is met while the interrupt enable register bit is set to 1, an

interrupt request signal is sent to the interrupt controller.

• When the interrupt controller receives an interrupt request, it sets the interrupt request flag.

• From among the interrupts with interrupt request flags set to 1, the interrupt controller selects

the interrupt request with the highest priority and holds the others pending. (Refer to table 3.2

for a list of interrupt priorities.)

• The interrupt controller checks the I bit of CCR. If the I bit is 0, the selected interrupt request

is accepted; if the I bit is 1, the interrupt request is held pending.

• If the interrupt is accepted, after processing of the current instruction is completed, both PC

and CCR are pushed onto the stack. The state of the stack at this time is shown in figure 3.4.

The PC value pushed onto the stack is the address of the first instruction to be executed upon

return from interrupt handling.

• The I bit of CCR is set to 1, masking further interrupts.

• The vector address corresponding to the accepted interrupt is generated, and the interrupt

handling routine located at the address indicated by the contents of the vector address is

executed.

Notes: 1. When disabling interrupts by clearing bits in an interrupt enable register, or when

clearing bits in an interrupt request register, always do so while interrupts are masked

(I = 1).

2. If the above clear operations are performed while I = 0, and as a result a conflict arises

between the clear instruction and an interrupt request, exception processing for the

interrupt will be executed after the clear instruction has been executed.

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