R8C/13 Group
10.1 Interrupt Overview
• Interrupt Sequence
An interrupt sequence — what are performed over a period from the instant an interrupt is accepted
to the instant the interrupt routine is executed — is described here.
If an interrupt occurs during execution of an instruction, the processor determines its priority when
the execution of the instruction is completed, and transfers control to the interrupt sequence from the
next cycle. If an interrupt occurs during execution of either the SMOVB, SMOVF, SSTR or RMPA
instruction, the processor temporarily suspends the instruction being executed, and transfers control
to the interrupt sequence.
The CPU behavior during the interrupt sequence is described below. Figure 10.4 shows time re-
quired for executing the interrupt sequence.
(1) The CPU gets interrupt information (interrupt number and interrupt request priority level) by read-
ing the address 0000016. Then it clears the IR bit for the corresponding interrupt to “0” (interrupt
not requested).
(2) The FLG register immediately before entering the interrupt sequence is saved to the CPU internal
(1)
temporary register
.
(3) The I, D and U flags in the FLG register become as follows:
The I flag is cleared to “0” (interrupts disabled).
The D flag is cleared to “0” (single-step interrupt disabled).
The U flag is cleared to “0” (ISP selected).
However, the U flag does not change state if an INT instruction for software interrupt numbers 32 to
63 is executed.
(1)
(4) The CPU’s internal temporary register is saved to the stack.
(5) The PC is saved to the stack.
(6) The interrupt priority level of the accepted interrupt is set in the IPL.
(7) The start address of the relevant interrupt routine set in the interrupt vector is stored in the PC.
After the interrupt sequence is completed, the processor resumes executing instructions from the start
address of the interrupt routine.
NOTES:
1. This register cannot be used by user.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
CPU clock
Address
000016
VEC+2
Address bus
Indeterminate
VEC
VEC+1
PC
SP-2 SP-1 SP-4
SP-2 SP-4
SP-3
VEC
contents
contents contents
Interrupt
information
VEC+1
contents
SP-3
VEC+2
contents
Indeterminate
Indeterminate
Data bus
RD
contents
SP-1
contents
WR
The indeterminate state depends on the instruction queue buffer. A read cycle occurs when the instruction queue buffer is ready
to accept instructions.
Figure 10.4 Time Required for Executing Interrupt Sequence
Rev.1.20 Jan 27, 2006 page 55 of 205
REJ09B0111-0120
RENESAS [ RENESAS TECHNOLOGY CORP ]
