R26 datasheet(138/487 Pages) RENESAS

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R8C/26 Group, R8C/27 Group

12. Interrupts

Rev.2.10

Sep 26, 2008

Page 119 of 453

REJ09B0278-0210

12.1.6.4

Interrupt Sequence

An interrupt sequence is performed between an interrupt request acknowledgement and interrupt routine

execution.

When an interrupt request is generated while an instruction is being executed, the CPU determines its interrupt

priority level after the instruction is completed. The CPU starts the interrupt sequence from the following cycle.

However, for the SMOVB, SMOVF, SSTR, or RMPA instructions, if an interrupt request is generated while the

instruction is being executed, the MCU suspends the instruction to start the interrupt sequence. The interrupt

sequence is performed as indicated below.

Figure 12.6 shows the Time Required for Executing Interrupt Sequence.

(1) The CPU gets interrupt information (interrupt number and interrupt request level) by reading address

00000h. The IR bit for the corresponding interrupt is set to 0 (interrupt not requested).(2)

(2) The FLG register is saved to a temporary register(1) in the CPU immediately before entering the

interrupt sequence.

(3) The I, D and U flags in the FLG register are set as follows:

The I flag is set to 0 (interrupts disabled).

The D flag is set to 0 (single-step interrupt disabled).

The U flag is set to 0 (ISP selected).

However, the U flag does not change state if an INT instruction for software interrupt number 32 to 63

is executed.

(4) The CPU’s internal temporary register(1) is saved to the stack.

(5) The PC is saved to the stack.

(6) The interrupt priority level of the acknowledged interrupt is set in the IPL.

(7) The starting address of the interrupt routine set in the interrupt vector is stored in the PC.

After the interrupt sequence is completed, instructions are executed from the starting address of the interrupt

routine.

Figure 12.6

Time Required for Executing Interrupt Sequence

NOTES:

1. This register cannot be used by user.

2. Refer to 12.5 Timer RC Interrupt, Clock Synchronous Serial I/O with Chip Select Interrupts, and

I2C bus Interface Interrupt (Interrupts with Multiple Interrupt Request Sources) for the IR bit

operations of the timer RC Interrupt, Clock Synchronous Serial I/O with Chip Select Interrupt, and the

I2C bus Interface Interrupt.

678

CPU Clock

Address Bus

Data Bus

Address

0000h

Undefined

Interrupt

information

SP-2 SP-1

SP-4

SP-3

VEC

VEC+1

VEC+2

SP-2

contents

SP-1

contents

SP-4

contents

SP-3

contents

VEC

contents

VEC+1

contents

VEC+2

contents

The indeterminate state depends on the instruction queue buffer. A read cycle occurs when the instruction queue buffer is

ready to acknowledge instructions.

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