ST72F264G ST Microelectronics, ST72F264G Datasheet - Page 50

• Manufacturer Part Number: ST72F264G
• Description: (ST72F260G - ST72F264G) 8-BIT MCU
• Manufacturer: ST Microelectronics

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ST72260G, ST72262G, ST72264G
WATCHDOG TIMER (Cont’d)
Figure 34. Exact Timeout Duration (t
50/171
WHERE:
t
t
t
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
To calculate the minimum Watchdog Timeout (t
IF
To calculate the maximum Watchdog Timeout (t
IF
Note: In the above formulae, division results must be rounded down to the next integer value.
Example:
With 2ms timeout selected in MCCSR register
min0
max0
OSC2
(MCCSR Reg.)
WDGCR Register (Hex.)
Value of T[5:0] Bits in
CNT
CNT
4
TB1 Bit
= (LSB + 128) x 64 x t
U
= 16384 x t
= 125ns if f
0
0
1
1
.com
<
MSB
-------------
MSB
-------------
00
3F
4
4
(MCCSR Reg.)
OSC2
OSC2
TB0 Bit
THEN
ELSE
THEN
ELSE
0
1
0
1
=8 MHz
t max
Min. Watchdog
t min
t max
Timeout (ms)
OSC2
t min
1.496
=
=
t
Selected MCCSR
128
min
=
=
t m in0
t m ax0
t m in0
t m ax0
Timebase
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10ms
25ms
2ms
4ms
min
+
+
+
+
and t
16384
16384
16384
16384
Max. Watchdog
Timeout (ms)
max
128.552
2.048
t


max


MSB
CN T
CNT
)
min
C NT
CNT
max
20
49
4
8
):
):
–
–
t osc2
4 CNT
---------------- -
LSB
t osc2
MSB
4CNT
---------------- -
59
53
35
54
MSB




+
+
192
192
+
+
L SB
LSB
64
64
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4CNT
---------------- -
MSB
4CNT
---------------- -
MS B
t osc2
t o sc2
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