Kontron COMe Starterkit Eval T2 - Manual (Page 137)

COM Express Interfaces
2.22.5. Watchdog Timer
Figure 54: Watchdog Timer Event Latch Schematic
The Watchdog Timer (WDT) event signal is provided by the COM Express Module. The WDT
output is active-high. It is sourced from Module pin B27.
The WDT event can cause the system to reset by making appropriate Carrier Board connections.
It also may be possible to configure the Module to reset on a WDT event; check the
manufacturer's Module Users Guide.
If the WDT output is used to cause a system reset, the WDT output will be cleared by the system
reset event.
The WDT can be latched to drive a LED for a visual indication of an event, as shown in this
example. The latch is only cleared by a complete power cycle.
PICMG ® COM Express ® Carrier Board Design Guide Rev. 2.0 / December 6, 2013
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V C C _ 3 V 3_SBY V C C _ 3 V 3_SBY
V C C _ 5 V V C C _ 5 V
C E X W D T
D 3 1
L E D R E D D 3 1
L E D R E D
C 2 3 6
1 0 0 n C 2 3 6
1 0 0 n R 1 8 6
1 0 k R 1 8 6
1 0 k
U 2 9
S N 7 4 L V C 7 4 A
U 2 9
S N 7 4 L V C 7 4 A
D 1 2
P R E 1 # 4
C L R 1 # 1
C L K 1 3
D 2
1 2
P R E 2 #
1 0
C L R 2 #
1 3
C L K 2
1 1
V C C
1 4
G N D
G N D 7
Q 2 9
Q 2 # 8
Q 1 5
Q 1 # 6
C 1 9 9
1 0 n / 5 0 V C 1 9 9
1 0 n / 5 0 V
R 1 8 5
1 5 0 k R 1 8 5
1 5 0 k
R 1 8 0
1 0 k R 1 8 0
1 0 k
U 1 4 0 4
A D M 8 1 1 4 .6 3
U 1 4 0 4
A D M 8 1 1 4 .6 3
1
R S T
2
M R
3
V C C 4
R 1 7 9
1 5 0 R R 1 7 9
1 5 0 R