Segment displays

1. 7-Segment Displays
Module M7.2
Section 6.5

2. Turning on an LED
+5V
R LED
G
A
Loutput pin
+5V
R LED
G
A
Loutput pin
1
0
+5V
+0.2V
+1.7V
No current
Current
light
no light
R =
voltage
current
=
5 -1.7
15 x10 -3 =220 ohms
Common
Anode

3. Turning on an LED
GAL output pin
0 V
R
No Current
LED
no light
GAL output pin
+5 V
R
Current
LED
light
R = voltage = 5 - 1.7 = 220 ohms
current 15 x 10^-3
+1.7 V 0 V
0 V
0
1 Common
Cathode
This is what
we use in Lab

4. 7-Segment Display

5. 7-Segment Display
a
b
c
d
e
f
g
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

6. 7-Segment Display
a
b
c
d
e
f
g
a b c d e f g
8 1 1 1 1 1 1 1
9 1 1 1 1 0 1 1
A 1 1 1 0 1 1 1
b 0 0 1 1 1 1 1
C 1 0 0 1 1 1 0
d 0 1 1 1 1 0 1
E 1 0 0 1 1 1 1
F 1 0 0 0 1 1 1

7. K-Map for Segment e

8. K-Map for Segment e
1
1
1 1
1
D3 D2
D1 D0
00 01 11 10
00
01
11
10
1
1
1
1
1
D3 & D2 D1 & !D0
!D2 & !D0
e = D3 & D2 # !D2 & !D0 # D3 & D1 # D1 & !D0
D3 & D1

9. 7seg.abl
MODULE seg7
TITLE '7 Segment Decoder, A. Student, 7/12/02'
DECLARATIONS
" INPUT PINS "
Z3..Z0 PIN 6,7,11,5; " Switch 1..4
Z = [Z3..Z0]; " 4-bit input vector
" OUTPUT PINS "
[A,B,C,D,E,F,G,DP] PIN 15,18,23,21,19,14,17,24 ISTYPE
'com';
Segments = [A,B,C,D,E,F,G]; “ 7-segment LED display
Z3..Z0
Can’t start
with numbers

10. EQUATIONS
@radix 16; " Identify the Hex Base
truth_table ( Z -> Segments ) " 7-segment display
0 -> 7E;
1 -> 30;
2 -> 6D;
3 -> 79;
4 -> 33;
5 -> 5B;
6 -> 5F;
7 -> 70;
8 -> 7F;
9 -> 7B;
0A -> 77;
0B -> 1F;
0C -> 4E;
0D -> 3D;
0E -> 4F;
0F -> 47;
END seg7
7seg.abl (cont’d)
HEX
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
A 1 1 1 0 1 1 1
b 0 0 1 1 1 1 1
C 1 0 0 1 1 1 0
d 0 1 1 1 1 0 1
E 1 0 0 1 1 1 1
F 1 0 0 0 1 1 1