st72f321r STMicroelectronics, st72f321r Datasheet - Page 54

• Manufacturer Part Number: st72f321r
• Description: 64/44-pin 8-bit Mcu With 32 To 60k Flash/rom, Adc, Five Timers, Spi, Sci, I2c Interface
• Manufacturer: STMicroelectronics

ST72321
WATCHDOG TIMER (Cont’d)
Figure 35. Exact Timeout Duration (t
54/189
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
TB1 Bit
= (LSB + 128) x 64 x t
= 16384 x t
= 125ns if f
0
0
1
1
<
MSB
-------------
MSB
-------------
3F
00
4
4
(MCCSR Reg.)
OSC2
OSC2
TB0 Bit
THEN
ELSE
THEN
ELSE
0
1
0
1
=8 MHz
t
Min. Watchdog
t
max
t
min
Timeout (ms)
OSC2
t
max
min
1.496
=
=
t
Selected MCCSR
128
min
=
=
t
t
min0
max0
t
t
Timebase
min0
max0
10ms
25ms
2ms
4ms
min
+
+
+
+
and t
16384
16384
16384
16384
Max. Watchdog
Timeout (ms)
max
128.552
2.048
t
max
MSB
CNT
CNT
)
min
CNT
CNT
max
20
49
4
8
):
):
–
–
t
4CNT
---------------- -
LSB
MSB
t
osc2
4CNT
---------------- -
59
53
35
54
osc2
MSB
+
+
192
192
+
+
LSB
LSB
64
64
4CNT
---------------- -
MSB
4CNT
---------------- -
MSB
t
t
osc2
osc2