HD6433044 Hitachi Semiconductor, HD6433044 Datasheet - Page 90

• Manufacturer Part Number: HD6433044
• Description: (HD64 Series) Hitachi Single-Chip Microcomputer
• Manufacturer: Hitachi Semiconductor

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).
ø
RES
Internal
address bus
Internal
read signal
Internal
write signal
Internal
data bus
(16 bits wide)
(1), (3)
(2), (4)
(5)
(6)
Address of reset vector ((1) = H'000000, (2) = H'000002)
Start address (contents of reset vector)
Start address
First instruction of program
Figure 4-4 Reset Sequence (Mode 5, 6 and 7)
(1)
(2)
Vector fetch
76
(4)
(3)
Internal
processing
Prefetch of
first program
instruction
(6)
(5)