SH7261 datasheet(666/1348 Pages) RENESAS

666 / 1348 page

Section 14 Watchdog Timer (WDT)

Rev. 2.00 Sep. 07, 2007 Page 634 of 1312

REJ09B0320-0200

14.4.3

Using Watchdog Timer Mode

1. Set the WT/

IT bit in WTCSR to 1, the type of count clock in the CKS[2:0] bits in WTCSR,

whether this LSI is to be reset internally or not in the RSTE bit in WRCSR, the reset type if it

is generated in the RSTS bit in WRCSR, and the initial value of the counter in WTCNT.

2. Set the TME bit in WTCSR to 1 to start the count in watchdog timer mode.

3. While operating in watchdog timer mode, rewrite the counter periodically to H'00 to prevent

the counter from overflowing.

4. When the counter overflows, the WDT sets the WOVF flag in WRCSR to 1, and the

WDTOVF signal is output externally (figure 14.4). The WDTOVF signal can be used to reset

the system. The

WDTOVF signal is output for 64 × Pφ clock cycles.

5. If the RSTE bit in WRCSR is set to 1, a signal to reset the inside of this LSI can be generated

simultaneously with the

WDTOVF signal. Either power-on reset or manual reset can be

selected for this interrupt by the RSTS bit in WRCSR. The internal reset signal is output for

128

× Pφ clock cycles.

6. When a WDT overflow reset is generated simultaneously with a reset input on the

RES pin,

the

RES pin reset takes priority, and the WOVF bit in WRCSR is cleared to 0.

H'FF

H'00

Overflow

H'00 written

in WTCNT

Internal

reset signal*

WDTOVF

signal

WTCNT value

WDTOVF and internal reset generated

WT/

IT:

TME:

Timer mode select bit

Timer enable bit

H'00 written

in WTCNT

Time

128

× Pφ clock cycles

Note: * Internal reset signal occurs only when the RSTE bit is set to 1.

[Legend]

WT/

IT = 1

TME = 1

WT/

IT = 1

TME = 1

WOVF = 1

Figure 14.4 Operation in Watchdog Timer Mode

SH7261 Datasheet(PDF) 666 Page - Renesas Technology Corp

SH7261 Datasheet(HTML) 666 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