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φ
RES
Internal address bus
Internal read signal
Internal write signal
Internal data bus
(1)
: Reset exception vector address ((1) = H'0000 or H'000000)
(2)
: Start address (contents of reset exception vector address)
(3)
: Start address ((3) = (2))
(4)
: First program instruction
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).
Figure 5.2 Reset Sequence (Mode 1)
Vector
Internal
Fetch of first program
fetch
processing
instruction
(1)
High level
(2)
Rev. 1.0, 02/00, page 91 of 1141
(3)
(4)
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