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M
1
6
C
2 /
6
A
G
o r
u
p
(
M
1
6
Digital Debounce Filter
Clock
f
8
Port In
P8
/ P1
5
7
Reload Value
Data Bus
(write)
f
8
Reload Value
FF
Port In
Signal Out
Count Value
FF
1
Reload Value
03
(continued)
Port In
(continued)
Signal Out
(continued)
Count Value
FF
(continued)
1. (Condition after reset). Reload = FF, Port In = signal Out continuosly.
2. Reload = 03. At edge of Port In != Signal Out, Counter gets Reload Value and
stats counting down.
3. Port In = Signal Out, counting stops.
4. At edge of Port In != Signal Out, Counter gets Reload Value and starts counting.
5. Counter underflows, stops, and Port In is driven to Signal Out.
6. At edge of Port In != Signal Out, counter gets Reload Value and starts counting.
7. Counter underflows, stops, and Port In is driven to Signal Out.
8. At edge of Port In != Signal Out, counter gets Reload Value and starts counting.
9. FF is written to Reload Value. Counter is stopped and loaded with FF.
Port In = Signal Out continuously.
Figure 16.6.2. Functioning of Digital Debounce Filter
R
e
. v
2
0 .
0
F
e
b
1 .
, 5
2
0
0
7
R
E
J
0
9
B
0
2
0
2
0 -
2
0
0
C
2 /
6
, A
M
1
6
C
2 /
6
, B
M
1
6
Signal Out
Count Value
(read)
03
03
2
01
03
02
00
6
7
page 228
f o
3
2
9
C
2 /
6
) T
To NMI and SD / INT5 and INPC17
Data Bus
02
01
03
3
4
FF
FF
03
02
FF
8
9
16. Programmable I/O Ports
02
01
00
FF
5
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