M30620FCAFP datasheet(471/615 Pages) RENESAS

471 / 615 page

Mitsubishi microcomputers

M16C / 62A Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Watchdog Timer

2-154

2.11.1 Overview of the watchdog timer usage

The watchdog timer can detect a runaway program using its 15-bit timer prescaler. The following is an

overview of the watchdog timer usage.

(1) Watchdog timer start procedure

When reset, the watchdog timer is in stopped state. Writing to the watchdog timer start register

initializes the watchdog timer to 7FFF16 and causes it to start performing a down count. The watchdog

timer, once started operating, cannot be stopped by any means other than stopping conditions.

(2) Watchdog timer stop conditions

The watchdog timer stops in any one of the following states:

(a) Period in which the CPU is in stopped state

(b) Period in which the CPU is in waiting state

(3) Watchdog timer initialization

The watchdog timer is initialized to 7FFF16 in the cases given below, and begins a down count.

(a) When the watchdog timer writes to the watchdog timer start register while a count is in progress

(b) When the watchdog timer underflows

(4) Runaway detection

When the watchdog timer underflows, a watchdog timer interrupt occurs. In writing a program, write to

the watchdog timer start register before the watchdog timer underflows. The watchdog timer interrupt

occurs regardless of the status of the interrupt enable flag (I flag). In processing a watchdog timer

interrupt, set the software reset bit to “1” to reset software.

(5) Watchdog timer cycle

The watchdog timer cycle varies depending on the BCLK and the frequency division ratio of the

prescaler selected.

2.11 Watchdog Timer Usage

CM07

CM06

CM17

CM16

BCLK

WDC7

Period

016MHz

8MHz

4MHz

1MHz

Invalid

2MHz

Invalid

32kHz

Invalid

Approx. 32.8ms (Note)

Approx. 262.1ms (Note)

Approx. 65.5ms (Note)

Approx. 524.3ms (Note)

Approx. 131.1ms (Note)

Approx. 1.049s (Note)

Approx. 524.3ms (Note)

Approx. 4.194s (Note)

Approx. 262.1ms (Note)

Approx. 2.097s (Note)

Approx. 2s (Note)

Note: An error due to the prescaler occurs.

Table 2.11.1. The watchdog timer cycle

M30620FCAFP Datasheet(PDF) 471 Page - Renesas Technology Corp

M30620FCAFP Datasheet(HTML) 471 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

Datasheet Download

Link URL