Renesas Hitachi H8S/2191, Hardware Manual, Page: 118 / 1065

Rev. 2.0, 11/00, page 91 of 1037
RES
Internal address bus
Internal read signal
Internal write signal
Internal data bus
Vector
fetch
(1)
(2)
(3)
(4) : Reset exception vector address ((1) = H'0000 or H'000000)
: Start address (contents of reset exception vector address)
: Start address ((3) = (2))
: First program instruction
(1) (3)
High level
Internal
processing
Fetch of first program
instruction
(2) (4)
Figure 5.2 Reset Sequence (Mode 1)
5.2.3 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).