T89C51RD2-RDTIL datasheet(47/104 Pages) ATMEL

47 / 104 page

T89C51RD2

4243G–8051–05/03

Reset value XXXX X000

WDT During Power Down and

Idle

In Power Down mode the oscillator stops, which means the WDT also stops. While in

Power Down mode the user does not need to service the WDT. There are 2 methods of

exiting Power Down mode: by a hardware reset or via a level activated external interrupt

which is enabled prior to entering Power Down mode. When Power Down is exited with

hardware reset, servicing the WDT should occur as it normally should whenever the

T89C51RD2 is reset. Exiting Power Down with an interrupt is significantly different. The

interrupt is held low long enough for the oscillator to stabilize. When the interrupt is

brought high, the interrupt is serviced. To prevent the WDT from resetting the device

while the interrupt pin is held low, the WDT is not started until the interrupt is pulled high.

It is suggested that the WDT be reset during the interrupt service routine.

To ensure that the WDT does not overflow within a few states of exiting of powerdown, it

is best to reset the WDT just before entering powerdown.

In the Idle mode, the oscillator continues to run. To prevent the WDT from resetting the

T89C51RD2 while in Idle mode, the user should always set up a timer that will periodi-

cally exit Idle, service the WDT, and re-enter Idle mode.

If the WDT is activated, the power consumption in stand-by mode will be above the

specified value.

WDT Time-out select bit 0

S0Selected Time-out

000(214 - 1) machine cycles, 16.3 ms @ 12 MHz

001(2

15 - 1) machine cycles, 32.7 ms @ 12 MHz

010(2

16 - 1) machine cycles, 65.5 ms @ 12 MHz

011(217 - 1) machine cycles, 131 ms @ 12 MHz

100(2

18 - 1) machine cycles, 262 ms @ 12 MHz

101(2

19 - 1) machine cycles, 542 ms @ 12 MHz

110(220 - 1) machine cycles, 1.05 s @ 12 MHz

111(2

21 - 1) machine cycles, 2.09 s @ 12 MHz

Bit

Number

Bit

Mnemonic

Description

T89C51RD2-RDTIL Datasheet(PDF) 47 Page - ATMEL Corporation

T89C51RD2-RDTIL Datasheet(HTML) 47 Page - ATMEL Corporation

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