H8S39 Datasheet, PDF (148/1512 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2600 Series

Section 4 Exception Handling
H8S/2639, H8S/2638, H8S/2636,
H8S/2630, H8S/2635 Group
Vector
fetch
Internal Prefetch of first program
processing instruction
*
*
*
φ
RES
Address bus
(1)
(3)
(5)
RD
HWR, LWR
D15 to D0
High
(2)
(4)
(6)
(1) (3) Reset exception handling vector address (when reset, (1) = H'000000,
(3) = H'000002)
(2) (4) Start address (contents of reset exception handling vector address)
(5) Start address ((5) = (2) (4))
(6) First program instruction
Note: * 3 program wait states are inserted.
Figure 4-3 Reset Sequence (Mode 4)
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).
Page 98 of 1458
REJ09B0103-0800 Rev. 8.00
May 28, 2010