1 watchdog programming – Rainbow Electronics T89C51AC2 User Manual
Page 66
66
T89C51AC2
Rev. B – 19-Dec-01
14.1 WatchDog
Programming
The three lower bits (S0, S1, S2) located into WDTPRG register permit to program the
WDT duration.
Table 32. Machine Cycle Count
To compute WD Time-Out, the following formula is applied:
Note:
Svalue represents the decimal value of (S2 S1 S0)
The following table describes the computed Time-Out value for Fosc
XTAL
= 12MHz in X1
mode
Table 33. Time-Out Computation
S2
S1
S0
Machine Cycle Count
0
0
0
2
14
- 1
0
0
1
2
15
- 1
0
1
0
2
16
- 1
0
1
1
2
17
- 1
1
0
0
2
18
- 1
1
0
1
2
19
- 1
1
1
0
2
20
- 1
1
1
1
2
21
- 1
S2
S1
S0
Fosc=12MHz
Fosc=16MHz
Fosc=20MHz
0
0
0
16.38 ms
12.28 ms
9.82 ms
0
0
1
32.77 ms
24.57 ms
19.66 ms
0
1
0
65.54 ms
49.14 ms
39.32 ms
0
1
1
131.07 ms
98.28 ms
78.64 ms
1
0
0
262.14 ms
196.56 ms
157.28 ms
1
0
1
524.29 ms
393.12 ms
314.56 ms
1
1
0
1.05 s
786.24 ms
629.12 ms
1
1
1
2.10 s
1.57 s
1.25 ms
FTime
Out
F
w d
12
2
14
2
Svalue
Ч
(
)
1
–
(
)
Ч
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=
–