4501 datasheet(148/212 Pages) RENESAS

148 / 212 page

2.3 Timers

2-31

4501 Group

APPLICATION

Rev.2.01

Feb 07, 2005

REJ09B0192-0201

Fig. 2.3.8 Watchdog timer setting example

••

Main routine (every 20 ms)

➀ Reset Flag WDF1

Watchdog timer flag WDF1 is reset.

“0”

Watchdog timer flag WDF1 cleared

(WRST instruction)

Main routine execution

Repeat

Do not clear watchdog timer flag WDF1 in interrupt service routine.

Interrupt may be executed even if program run-away occurs.

When going to RAM back-up mode

WRST

; WDF flag cleared

NOP

; Interrupt disabled

EPOF

; POF instruction enabled

POF

↓

Oscillation stop (RAM back-up mode)

In the RAM back-up mode, WEF, WDF1 and WDF2 flags are initialized. However, when WDF2 flag is set to “1”, at the

same time, system enters RAM back-up mode, microcomputer may be reset. When watchdog timer and RAM back-up

mode are used, execute the WRST instruction before system enters the RAM back-up mode to initialize WDF1 flag.

Note when the watchdog timer flag is cleared

When ➀ is executed, considering the skip of the next instruction according to the

watchdog timer flag WDF1, insert the NOP instruction after the WRST instruction.

2.3.4 Notes on use

(1)

Prescaler

Stop the prescaler operation to change its frequency dividing ratio.

(2)

Count source

Stop timer 1 or 2 counting to change its count source.

(3)

Reading the count values

Stop timer 1 or 2 counting and then execute the TAB1 or TAB2 instruction to read its data.

4501 Datasheet(PDF) 148 Page - Renesas Technology Corp

4501 Datasheet(HTML) 148 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