ST72521 STMICROELECTRONICS [STMicroelectronics], ST72521 Datasheet - Page 55

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ST72521

Manufacturer Part Number
ST72521
Description
8-BIT MCU WITH NESTED INTERRUPTS, FLASH, 10-BIT ADC, FIVE TIMERS, SPI, SCI, I2C, CAN INTERFACE
Manufacturer
STMICROELECTRONICS [STMicroelectronics]
Datasheet

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WATCHDOG TIMER (Cont’d)
Figure 34. Exact Timeout Duration (t
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
WDGCR Register (Hex.)
(MCCSR Reg.)
Value of T[5:0] Bits in
CNT
CNT
TB1 Bit
= (LSB + 128) x 64 x t
= 16384 x t
= 125ns if f
0
0
1
1
<
MSB
-------------
MSB
-------------
00
3F
4
4
(MCCSR Reg.)
OSC2
OSC2
TB0 Bit
THEN
ELSE
THEN
ELSE
0
1
0
1
=8 MHz
Min. Watchdog
t
Timeout (ms)
t min
max
OSC2
t
t
ma x
m in
1.496
t
Selected MCCSR
128
min
=
=
=
=
t min0
t
Timebase
max0
t
t
min0
max0
10ms
25ms
2ms
4ms
min
+
+
+
+
and t
16384
16384
16384
16384
Max. Watchdog
Timeout (ms)
max
128.552
2.048
t
max
CNT
MSB
)
min
C NT
CN T
max
20
49
C NT
4
8
):
):
t
t
osc2
LSB
osc2
4 CNT
---------------- -
MSB
59
53
35
54
4CNT
---------------- -
MSB
+
+
192
192
+
+
LS B
LSB
64
64
4CNT
---------------- -
MSB
4CNT
---------------- -
MSB
ST72521
t osc2
t osc2
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