R8C datasheet(24/199 Pages) RENESAS

24 / 199 page

R8C/10 Group

5. Reset

Rev.1.20 Jan 27, 2006

page 14 of 180

REJ09B0019-0120

5. Reset

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

5.1 Hardware Reset

____________

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

oscillator clock divided by 8 is automatically selected for the CPU. 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. 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 ✕ 20).

____________

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

• Power on

____________

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

(2) Let the power supply voltage increase until it meets the recommended operating condition.

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

(4) Wait for 500 µs (1/fRING ✕ 20).

____________

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

5.3 Watchdog Timer Reset

Where the PM12 bit in the PM1 register is “1” (reset when watchdog timer underflows), the microcom-

puter initializes its pins, CPU and SFR if the watchdog timer underflows. Then the program is ex-

ecuted starting from the address indicated by the reset vector. After reset, the on-chip oscillator clock

divided by 8 is automatically selected for the CPU.

____________

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

Status

CNVSS = VSS

Pin name

P30 to P33, P37

P45 to P47

Input port

5.2 Software Reset

When the PM03 bit in the PM0 register is set to “1” (microcomputer reset), the microcomputer has its

pins, CPU, and SFR initialized. Then the program is executed starting from the address indicated by

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

CPU.

R8C датащи(PDF) 24 Page - Renesas Technology Corp

R8C датащи(HTML) 24 Page - Renesas Technology Corp

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

датащи скачать

ссылки URL