H838532H datasheet(80/508 Pages) RENESAS

Nome de Peças	H838532H

Descrição Electrónicos	16-Bit Single-Chip Microcomputer H8 Family / H8/300H Super Low Power Series

PDF	508 Pages

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Fabricante Electrônico	RENESAS [Renesas Technology Corp]

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Section 3 Exception Handling

Rev. 1.00 May 30, 2008 Page 60 of 484

REJ09B0436-0100

When system power is turned on or off, the

RES pin should be held low.

Figure 3.1 shows the reset sequence starting from

RES input.

Vector fetch

Internal

address bus

Internal read

signal

Internal write

signal

Internal data

bus (16-bit)

RES

Internal

processing

Program initial

instruction prefetch

(1) Reset exception handling vector address (H'0000)

(2) Program start address

(3) First instruction of program

(2)

(3)

(2)

(1)

Reset cleared

Figure 3.1 Reset Sequence

3.2.3

Interrupt Immediately after Reset

After a reset, if an interrupt were to be accepted before the stack pointer (SP: R7) was initialized,

PC and CCR would not be pushed onto the stack correctly, resulting in program runaway. To

prevent this, immediately after reset exception handling all interrupts are masked. For this reason,

the initial program instruction is always executed immediately after a reset. This instruction should

initialize the stack pointer (e.g. MOV.W #xx: 16, SP).

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