HD643303x Hitachi, HD643303x Datasheet - Page 84

• Manufacturer Part Number: HD643303x
• Description: Hitachi Microcomputer
• Manufacturer: Hitachi

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
Address bus
RD
WR
D
(1), (3)
(2), (4)
(5)
(6)
Note: After a reset, the wait-state controller inserts three wait states in every bus cycle.
15
to D
0
Address of reset vector: (1) = H'00000, (3) = H'00002
Start address (contents of reset vector)
Start address
First instruction of program
High
Figure 4-3 Reset Sequence (Mode 2)
(2)
(1)
Vector fetch
69
(4)
(3)
Internal
processing
(6)
(5)
Prefetch of first
program instruction