Ibm uPD78082 Manual do Utilizador descarregar pdf (Página 133)

110

CHAPTER 7 WATCHDOG TIMER

7.4.2 Interval timer operation

The watchdog timer operates as an interval timer which generates interrupt requests repeatedly at an interval of

the preset count value when bit 4 (WDTM4) of the watchdog timer mode register (WDTM) is set to 0.

A count clock (interval time) can be selected by the bits 0 to 2 (TCL20 to TCL22) of the timer clock select register

2 (TCL2). By setting the bit 7 (RUN) of WDTM to 1, the watchdog timer starts operating as an interval timer.

When the watchdog timer operated as interval timer, the interrupt mask flag (TMMK4) and priority specify flag

(TMPR4) are validated and the maskable interrupt request (INTWDT) can be generated. Among maskable interrupt

requests, the INTWDT default has the highest priority.

The interval timer continues operating in the HALT mode but it stops in STOP mode. Thus, set bit 7 (RUN) of

WDTM to 1 before the STOP mode is set, clear the interval timer and then execute the STOP instruction.

Cautions 1. Once bit 4 (WDTM4) of WDTM is set to 1 (with the watchdog timer mode selected), the interval

timer mode is not set unless RESET input is applied.

2. The interval time just after setting with WDTM may be shorter than the set time by a maximum

of 0.5 %.

Table 7-5. Interval Timer Interval Time

TCL22 TCL21 TCL20 Interval Time MCS = 1 MCS = 0

000 2

× 1/fXX 2

× 1/fX (410

s) 2

× 1/fX (819

001 2

× 1/fXX 2

× 1/fX (819

s) 2

× 1/fX (1.64 ms)

010 2

× 1/fXX 2

× 1/fX (1.64 ms) 2

× 1/fX (3.28 ms)

011 2

× 1/fXX 2

× 1/fX (3.28 ms) 2

× 1/fX (6.55 ms)

100 2

× 1/fXX 2

× 1/fX (6.55 ms) 2

× 1/fX (13.1 ms)

101 2

× 1/fXX 2

× 1/fX (13.1 ms) 2

× 1/fX (26.2 ms)

110 2

× 1/fXX 2

× 1/fX (26.2 ms) 2

× 1/fX (52.4 ms)

111 2

× 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 ... 128 129 130 131 132 133 134 135 136 137 138 ... 273 274

Comentários a estes Manuais

Sem comentários

Ibm uPD78082 Manual do Utilizador Página 133

Comentários a estes Manuais

Manuais e produtos relacionados com Hardware Ibm uPD78082