Digilent DIO1 - Manual (Page 3)

Digilent DIO1 Reference Manual Digilent, Inc.
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are driven for 4ms in an endless succession, the
display will show “17” in the first two digits.
An example timing diagram is provided to the
right.
.
Push Buttons
The 5 momentary-contact push buttons are
normally high when unused; this high signal is
translated to a low signal by a Schmitt Trigger.
When the button is actively pressed the signal
is driven low, which the Schmitt Trigger will
translate to a high signal. The buttons exhibit a
worst-case bounce time of about 1ms. A
74HC14 Hex Schmitt Trigger inverter provides
the debounce filtering and ESD protection. The
button outputs are brought out directly to pins
on interface connector B.
a1
Cathodes -- connected to
CPLD pins via 100
Ω resistor
Anodes -- connected to CPLD
via transistors for greater current
Vdd
a b c d e f g dp
a2 a3 a4
AN1
AN2
AN3
AN4
Cathodes Digit 1 Digit 2 Digit 3 Digit 4
Refresh period = 1ms to 16ms
Digit period = Refresh / 4
Seven segment display refresh signals and timings
Figure 3. (a) Seven segment display detail.
(b) common anode display configuration. (c)
segement illumination patterns for decimal
digits. ( d) segment illumination truth table.
Common anode
a
f
e
d
c
b
g
a f g e d c b
(a) (b)
(c)
Digit Illuminated Segment
Show
n
a b c d e f g
0
1 1 1 1 1 1 0
1
0 1 1 0 0 0 0
2
1 1 0 1 1 0 1
3
1 1 1 1 0 0 1
4
0 1 1 0 0 1 1
5
1 0 1 1 0 1 1
6
1 0 1 1 1 1 1
7
1 1 1 0 0 0 0
8
1 1 1 1 1 1 1
9
1 1 1 1 0 1 1
(d)
GND
4.7KOhm
To Connector
.01uF
GND
VCC