Ibm uPD78082 Manual do Utilizador descarregar pdf (Página 126)

103

CHAPTER 7 WATCHDOG TIMER

7.1 Watchdog Timer Functions

The watchdog timer has the following functions.

• Watchdog timer

• Interval timer

Caution Select the watchdog timer mode or the interval timer mode with the watchdog timer mode register

(WDTM) (The watchdog timer and interval timer cannot be used at the same time).

(1) Watchdog timer mode

An inadvertent program loop is detected. Upon detection of the inadvertent program loop, a non-maskable

interrupt request or RESET can be generated.

Table 7-1. Watchdog Timer Overrun Detection Times

Runaway Detection Time MCS = 1 MCS = 0

× 1/fXX 2

× 1/fX (410

s) 2

× 1/fX (819

× 1/fXX 2

× 1/fX (819

s) 2

× 1/fX (1.64 ms)

× 1/fXX 2

× 1/fX (1.64 ms) 2

× 1/fX (3.28 ms)

× 1/fXX 2

× 1/fX (3.28 ms) 2

× 1/fX (6.55 ms)

× 1/fXX 2

× 1/fX (6.55 ms) 2

× 1/fX (13.1 ms)

× 1/fXX 2

× 1/fX (13.1 ms) 2

× 1/fX (26.2 ms)

× 1/fXX 2

× 1/fX (26.2 ms) 2

× 1/fX (52.4 ms)

× 1/fXX 2

× 1/fX (104.9 ms) 2

× 1/fX (209.7 ms)

Remarks 1. f

XX : Main system clock frequency (fX or fX/2)

2. f

X : Main system clock oscillation frequency

3. MCS : Oscillation mode selection register (OSMS) bit 0

4. Values in parentheses when operated at f

X = 5.0 MHz.

1 2 ... 121 122 123 124 125 126 127 128 129 130 131 ... 273 274

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