R5F3640MNFB datasheet(53/398 Pages) RENESAS

53 / 398 page

REJ09B0392-0064 Rev.0.64

Oct 12, 2007

Page 32 of 373

Under development

Preliminary Specification

Specification in this preliminary version is subject to change.

M16C/64 Group

5. Reset

Reset

Hardware reset 1, brown-out reset, software reset, watchdog timer reset and oscillation stop detection reset

are available to reset the microcomputer.

5.1

Hardware Reset 1

The microcomputer resets pins, the CPU, and SFR by setting the

RESET pin. If the supply voltage meets

the recommended operating conditions, the microcomputer resets all pins, the CPU, and SFR when an

“L” signal is applied to the

RESET pin (see Table 5.1 “Pin Status When RESET Pin Level is “L””).

When the signal applied to the

RESET pin changes low (“L”) to high (“H”), the microcomputer executes

the program in an address indicated by the reset vector. The 125 kHz on-chip oscillator clock divided by 8

is automatically selected as a CPU clock after reset.

Refer to 4. “Special Function Registers (SFRs)” for SFR states after reset.

The internal RAM is not reset. When an “L” signal is applied to the

RESET pin while writing data to the

internal RAM, the internal RAM is in an indeterminate state.

Figure 5.1 shows an Example Reset Circuit. Figure 5.2 shows a Reset Sequence. Table 5.1 lists Pin Sta-

tus When

RESET Pin Level is “L”.

5.1.1

Reset on a Stable Supply Voltage

(1) Apply “L” to the

RESET pin

(2) Wait for 1/fOCO-S × 20

(3) Apply an “H” signal to the

RESET pin

5.1.2

Power-on Reset

(1) Apply “L” to the

RESET pin

(2) Raise the supply voltage to the recommended operating level

(3) Insert td(P-R) ms as wait time for the internal voltage to stabilize

(4) Wait for 1/fOCO-S × 20

(5) Apply “H” to the

RESET pin

Figure 5.1

Example Reset Circuit

RESET

VCC1

RESET

VCC1

Recommended

operation

voltage

td (P-R)+

x 20 or above

0.2 VCC1 or below

fOCO - S

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