Table 2. threshold suffix guide, Table 3. watchdog timeout – Rainbow Electronics MAX6869 User Manual
Page 13
input at different points in the program, rather than
pulsing the watchdog input high-low-high or low-high-
low. This technique avoids a stuck loop, in which the
watchdog timer would continue to be reset inside the
loop, keeping the watchdog from timing out.
Figure
6 shows an example of a flow diagram where
the I/O driving the watchdog input is set high at the
beginning of the program, set low at the beginning of
every subroutine or loop, then set high again when the
program returns to the beginning. If the program
should hang in any subroutine, the problem would
quickly be corrected, since the I/O is continually set low
and the watchdog timer is allowed to time out, causing
a reset or interrupt to be issued.
MAX6854–MAX6869
Nanopower µP Supervisory Circuits with
Optional Manual Reset, Watchdog Timer
______________________________________________________________________________________
13
START
SET WDI
HIGH
PROGRAM
CODE
SUBROUTINE OR
PROGRAM LOOP
SET WDI LOW
RETURN
V
CC
THRESHOLD FALLING
SUFFIX
MIN
TYP
MAX
UNITS
46
4.509
4.625
4.741
45
4.388
4.500
4.613
44
4.266
4.375
4.484
43
4.193
4.300
4.408
42
4.095
4.200
4.305
41
3.998
4.100
4.203
40
3.900
4.000
4.100
39
3.802
3.900
3.998
38
3.705
3.800
3.895
37
3.608
3.700
3.793
36
3.510
3.600
3.690
35
3.413
3.500
3.588
34
3.315
3.400
3.485
33
3.218
3.300
3.383
32
3.120
3.200
3.280
31
2.998
3.075
3.152
30
2.925
3.000
3.075
29
2.852
2.925
2.998
28
2.730
2.800
2.870
27
2.633
2.700
2.768
26
2.559
2.625
2.691
25
2.438
2.500
2.563
24
2.340
2.400
2.460
23
2.255
2.313
2.371
225
2.180
2.235
2.290
22
2.133
2.188
2.243
21
2.048
2.100
2.153
20
1.950
2.000
2.050
19
1.853
1.900
1.948
18
1.755
1.800
1.845
17
1.623
1.665
1.707
16
1.536
1.575
1.614
V
Figure
6. Watchdog Flow Diagram
Table
2. Threshold Suffix Guide
WATCHDOG TIMEOUT PERIOD
SUFFIX
MIN
TYP
MAX
UNITS
S
1.5
3.3
7.75
L
95
209
487
s
Table
3. Watchdog Timeout