HD64F2149 Datasheet, PDF (126/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

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RES
Address bus
RD
HWR, LWR
D15 to D8
Vector fetch
Internal
processing
Fetch of
first program
instruction
*
*
*
(1)
(3)
High
(2)
(4)
(5)
(6)
(1) (3) Reset exception vector address ((1) = H'0000, (3) = H'0001)
(2) (4) Start address (contents of reset exception vector address)
(5) Start address ((5) = (2) (4))
(6) First program instruction
Note: * 3 program wait states are inserted.
Figure 4.3 Reset Sequence (Mode 1)
4.2.3 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).
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