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