Datasheet

Section 4 Exception Handling
Rev. 4.00 Sep 27, 2006 page 108 of 1130
REJ09B0327-0400
Address bus
Vector fetch
Internal
processing
Fetch of
first program
instruction
(1) (3) Reset exception vector address ((1) = H'0000, (3) = H'0001)
(2) (4) Start address (contents of reset exception vector address)
(5) Start address ((5) = (2) (4))
(6) First program instruction
φ
RES
(1) (5)
High
(2) (4)
(3)
(6)
RD
HWR, LWR
D15 to D8
*
Note: * 3 program wait states are inserted.
**
Figure 4.3 Reset Sequence (Mode 1)
4.2.3 Interrupts after Reset
If an interrupt is accepted after a reset but before the stack pointer (SP) is initialized, the 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. Since the first instruction of a program is
always executed immediately after the reset state ends, make sure that this instruction initializes
the stack pointer (example: MOV.L #xx:32, SP).