M38C89MB datasheet(36/55 Pages) RENESAS

36 / 55 page

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS

38C8 Group

RESET CIRCUIT

To reset the microcomputer, RESET pin should be held at an “L”

level for 2 µs or more. Then the RESET pin is returned to an “H” level

(the power source voltage should be between VCC (min.) and 5.5 V,

and the quartz-crystal oscillator should be stable), reset is released.

After the reset is completed, the program starts from the address

contained in address FFFD16 (high-order byte) and address FFFC16

(low-order byte). Make sure that the reset input voltage is less than

0.2Vcc when a power source voltage passes VCC (min.).

Fig. 34 Reset sequence

Fig. 33 Reset circuit example

0.2VCC

Poweron

VCC

RESET

VCC

RESET

Power source

voltage detection

circuit

Power source

voltage

Reset input

voltage

RESET

Internal

reset

Address

Data

SYNC

XIN

FFFC

FFFD

ADH, ADL

ADL

ADH

????

XIN : about 8200 cycles

Notes 1: The frequency relation of f(XIN) and f(

φ) is f(XIN) = 8 • f(φ).

2: The question marks (?) indicate an undefined state that

depends on the previous state.

Reset address from

vector table

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