HD6432646 Hitachi, HD6432646 Datasheet - Page 128

• Manufacturer Part Number: HD6432646
• Description: (HD64F264x Series) 16-Bit Microcomputer
• Manufacturer: Hitachi

4.2.3
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).
94
(1) (3) Reset exception handling vector address (when reset, (1) = H'000000,
(2) (4) Start address (contents of reset exception handling vector address)
(5)
(6)
Note: * 3 program wait states are inserted.
Interrupts after Reset
Ø
RES
Address bus
RD
HWR, LWR
D15 to D0
(3) = H'000002)
Start address ((5) = (2) (4))
First program instruction
Figure 4-3 Reset Sequence (Mode 4)
(1)
*
(2)
Vector
fetch
High
*
processing
(3)
Internal
(4)
Prefetch of first program
instruction
*
(5)
(6)