ST72521AR9TC 查看數據表（PDF） - STMicroelectronics
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ST72521AR9TC
STMicroelectronics
ST72521AR9TC Datasheet PDF : 211 Pages
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ST72521
WATCHDOG TIMER (Cont’d)
Figure 34. Exact Timeout Duration (tmin and tmax)
WHERE:
tmin0 = (LSB + 128) x 64 x tOSC2
tmax0 = 16384 x tOSC2
tOSC2 = 125ns if fOSC2=8 MHz
CNT = Value of T[5:0] bits in the WDGCR register (6 bits)
MSB and LSB are values from the table below depending on the timebase selected by the TB[1:0] bits
in the MCCSR register
TB1 Bit
TB0 Bit
(MCCSR Reg.) (MCCSR Reg.)
0
0
0
1
1
0
1
1
Selected MCCSR
Timebase
2ms
4ms
10ms
25ms
MSB
4
8
20
49
LSB
59
53
35
54
To calculate the minimum Watchdog Timeout (tmin):
IF CNT < M------4S----B---
THEN tm in = tmin0 + 16384 × CNT × tosc2
ELSE
tmin
= tmin0 +
16384 × CN T –
4--M--C---S--N---B--T--
+
( 192
+
L S B)
×
64
×
4--M--C----S-N---B--T--
× tosc2
To calculate the maximum Watchdog Timeout (tmax):
IF CNT ≤
M------S----B---
4
THEN tma x = tmax0 + 16384 × C NT × tosc2
ELSE
tmax
= tmax0 +
16384 × C NT –
4--M--C----S-N---B--T--
+
( 192
+
LSB)
×
64
×
4--M--C----S-N---B--T--
× tosc2
Note: In the above formulae, division results must be rounded down to the next integer value.
Example:
With 2ms timeout selected in MCCSR register
Value of T[5:0] Bits in
WDGCR Register (Hex.)
00
3F
Min. Watchdog
Timeout (ms)
tmin
1.496
128
Max. Watchdog
Timeout (ms)
tmax
2.048
128.552
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