R8C13 datasheet(25/224 Pages) RENESAS

25 / 224 page

Rev.1.20

Jan 27, 2006

page 14 of 205

REJ09B0111-0120

R8C/13 Group

5. Reset

There are three types of resets: a hardware reset, a software reset, and an watchdog timer reset.

5.1 Hardware Reset

There are three kinds of hardware reset: hardware reset 1, hardware reset 2, and power-on reset.

After reset, the low-speed on-chip oscillator clock divided by 8 is automatically selected for the CPU.

5.1.1 Hardware Reset 1

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A reset is applied using the RESET pin. When an “L” signal is applied to the RESET pin while the

power supply voltage is within the recommended operating condition, the pins are initialized (see

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Table 5.1 “Pin Status When RESET Pin Level is 'L'”). When the input level at the RESET pin is

released from “L” to “H”, the CPU and SFR are initialized, and the program is executed starting

from the address indicated by the reset vector. Figure 5.1 shows the CPU register status after

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reset and figure 5.2 shows the reset sequence. The internal RAM is not initialized. If the RESET

pin is pulled “L” while writing to the internal RAM, the internal RAM becomes indeterminate.

Figures 5.3 to 5.4 show the reset circuit example using the hardware reset 1. Refer to Chapter 4,

“Special Function Register (SFR)” for the status of SFR after reset.

• When the power supply is stable

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(1) Apply an “L” signal to the RESET pin.

(2) Wait for 500 µs (1/fRING-S ✕ 20).

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(3) Apply an “H” signal to the RESET pin.

• Power on

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(1) Apply an “L” signal to the RESET pin.

(2) Let the power supply voltage increase until it meets the recommended operating condi-

tion.

(3) Wait td(P-R) or more until the internal power supply stabilizes.

(4) Wait for 500 µs (1/fRING-S ✕ 20).

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(5) Apply an “H” signal to the RESET pin.

Pin status

Pin name

P30 to P33, P37

P45 to P47

Input port

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Table 5.1 Pin Status When RESET Pin Level is “L”

5.1 Hardware Reset

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