Interrupts After Reset - Renesas H8/3067 Series User Manual

φ
RES
Internal
address bus
Internal
read signal
Internal
write signal
Internal
data bus
(16 bits wide)
(1) Address of reset vector (H'0000)
(2) Start address (contents of reset exception handling vector address)
(3) First instruction of program
4.2.3

Interrupts after Reset

If an interrupt is accepted after a reset but before the stack pointer (SP) is initialized, PC and CCR
will not be saved correctly, leading to a program crash. To prevent this, all interrupt requests,
including NMI, are disabled immediately after a reset. The first instruction of the program is
always executed immediately after the reset state ends. This instruction should initialize the stack
pointer (example: MOV.L #xx:32, SP).
Vector fetch
(1)
(2)
Figure 4.4 Reset Sequence (Mode 6)
Section 4 Exception Handling
Prefetch of
Internal
first program
processing
instruction
(2)
(3)
Rev. 4.00 Jan 26, 2006 page 85 of 938
REJ09B0276-0400