R8C11 datasheet(25/227 Pages) RENESAS

25 / 227 page

R8C/11 Group

Rev.1.20

Jan 27, 2006

page 14 of 204

REJ09B0062-0120

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

____________

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 initial-

____________

ized (see 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

____________

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

____________

(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).

____________

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

Status

Pin name

P30 to P33, P37

P45 to P47

Input port

____________

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

5.1 Hardware Reset

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