Rainbow Electronics T89C51AC2 - 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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