at90ls8535-8mi ATMEL Corporation, at90ls8535-8mi Datasheet - Page 50

• Manufacturer Part Number: at90ls8535-8mi
• Description: 8-bit Microcontroller With 8k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

50
AT90S/LS8535
1. In the same operation, write a logical “1” to WDTOE and WDE. A logical “1” must
2. Within the next four clock cycles, write a logical “0” to WDE. This disables the
• Bits 2..0 – WDP2, WDP1, WDP0: Watchdog Timer Prescaler 2, 1 and 0
The WDP2, WDP1 and WDP0 bits determine the Watchdog Timer prescaling when the
Watchdog Timer is enabled. The different prescaling values and their corresponding
time-out periods are shown in Table 21.
Table 21. Watchdog Timer Prescale Select
Note:
WDP2
be written to WDE even though it is set to “1” before the disable operation starts.
Watchdog.
0
0
0
0
1
1
1
1
The frequency of the Watchdog oscillator is voltage-dependent as shown in the Electrical
Characteristics section.
The WDR (Watchdog Reset) instruction should always be executed before the Watchdog
Timer is enabled. This ensures that the reset period will be in accordance with the
Watchdog Timer prescale settings. If the Watchdog Timer is enabled without reset, the
Watchdog Timer may not start to count from zero.
To avoid unintentional MCU resets, the Watchdog Timer should be disabled or reset
before changing the Watchdog Timer Prescale Select.
WDP1
0
0
1
1
0
0
1
1
WDP0
0
1
0
1
0
1
0
1
Number of WDT
Oscillator Cycles
16K cycles
32K cycles
64K cycles
128K cycles
256K cycles
512K cycles
1,024K cycles
2,048K cycles
0.38 s
0.75 s
Typical Time-out
at V
47 ms
94 ms
0.19 s
1.5 s
3.0 s
6.0 s
CC
= 3.0V
Typical Time-out
at V
15 ms
30 ms
60 ms
0.12 s
0.24 s
0.49 s
0.97 s
1.9 s
CC
= 5.0V
1041H–11/01