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Encoders
Module M9.3
Section 6.3
Encoders
• Encoders
• Priority Encoders
• TTL Encoders
Encoders
A
B
I0
I1
I2
I3
4-to-2 Encoder 1 0 0 0 0 0
0 1 0 0 0 10 0 1 0 1 00 0 0 1 1 1
I0 I1 I2 I3 B A
Encoders
1 0 0 0 0 00 1 0 0 0 10 0 1 0 1 00 0 0 1 1 1
I0 I1 I2 I3 B AAssume only 1 inputcan be high at any time.
A = I1 # I3B = I2 # I3
I1
I2I3
I0
B = I2 # I3
A = I1 # I3
8-to-3 Encoder
1 0 0 0 0 0 0 0 0 0 00 1 0 0 0 0 0 0 0 0 10 0 1 0 0 0 0 0 0 1 00 0 0 1 0 0 0 0 0 1 10 0 0 0 1 0 0 0 1 0 00 0 0 0 0 1 0 0 1 0 10 0 0 0 0 0 1 0 1 1 00 0 0 0 0 0 0 1 1 1 1
I0 I1 I2 I3 I4 I5 I6 I7 Y2 Y1 Y0
Y2 = I7 # I6 # I5 # I4Y1 = I7 # I6 # I3 # I2Y0 = I7 # I5 # I3 # I1
encoder.abl
MODULE encoder83
TITLE 'Encoder, D. Hanna, 7/15/02'
DECLARATIONS
" INPUT PINS "
I7..I0 PIN 6, 7, 11, 5, 72, 71, 66, 70; " Switch 1..8
" OUTPUT PINS "
Y2..Y0 PIN 37, 36, 35 ISTYPE 'com'; " LED 6..8
EQUATIONS
Y2 = I7 # I6 # I5 # I4;
Y1 = I7 # I6 # I3 # I2;
Y0 = I7 # I5 # I3 # I1;
END encoder83
1 0 0 0 0 0 0 0 0 0 00 1 0 0 0 0 0 0 0 0 10 0 1 0 0 0 0 0 0 1 00 0 0 1 0 0 0 0 0 1 10 0 0 0 1 0 0 0 1 0 00 0 0 0 0 1 0 0 1 0 10 0 0 0 0 0 1 0 1 1 00 0 0 0 0 0 0 1 1 1 1
I0 I1 I2 I3 I4 I5 I6 I7 Y2 Y1 Y01 0 0 0 0 0 0 0 0 0 00 1 0 0 0 0 0 0 0 0 10 0 1 0 0 0 0 0 0 1 00 0 0 1 0 0 0 0 0 1 10 0 0 0 1 0 0 0 1 0 00 0 0 0 0 1 0 0 1 0 10 0 0 0 0 0 1 0 1 1 00 0 0 0 0 0 0 1 1 1 1
I0 I1 I2 I3 I4 I5 I6 I7 Y2 Y1 Y0
Y2 = I7 # I6 # I5 # I4Y1 = I7 # I6 # I3 # I2Y0 = I7 # I5 # I3 # I1
Priority Encoder
1 0 0 0 0 0 0 0 0 0 0X 1 0 0 0 0 0 0 0 0 1X X 1 0 0 0 0 0 0 1 0X X X 1 0 0 0 0 0 1 1X X X X 1 0 0 0 1 0 0X X X X X 1 0 0 1 0 1X X X X X X 1 0 1 1 0X X X X X X X 1 1 1 1
I0 I1 I2 I3 I4 I5 I6 I7 Y2 Y1 Y0
Priority Encoder
1 0 0 0 0 0 0 0 0 0 0X 1 0 0 0 0 0 0 0 0 1X X 1 0 0 0 0 0 0 1 0X X X 1 0 0 0 0 0 1 1X X X X 1 0 0 0 1 0 0X X X X X 1 0 0 1 0 1X X X X X X 1 0 1 1 0X X X X X X X 1 1 1 1
I0 I1 I2 I3 I4 I5 I6 I7 Y2 Y1 Y0
Y2 = L7 # L6 # L5 # L4
L7 = I7L6 = !I7 & I6L5 = !I7 & !I6 & I5L4 = !I7 & !I6 & !I5 & I4
Priority Encoder
1 0 0 0 0 0 0 0 0 0 0X 1 0 0 0 0 0 0 0 0 1X X 1 0 0 0 0 0 0 1 0X X X 1 0 0 0 0 0 1 1X X X X 1 0 0 0 1 0 0X X X X X 1 0 0 1 0 1X X X X X X 1 0 1 1 0X X X X X X X 1 1 1 1
I0 I1 I2 I3 I4 I5 I6 I7 Y2 Y1 Y0
Y1 = L7 # L6 # L3 # L2
L7 = I7L6 = !I7 & I6L3 = !I7 & !I6 & !I5 & !I4 & I3L2 = !I7 & !I6 & !I5 & !I4 & !I3 & I2
Priority Encoder
1 0 0 0 0 0 0 0 0 0 0X 1 0 0 0 0 0 0 0 0 1X X 1 0 0 0 0 0 0 1 0X X X 1 0 0 0 0 0 1 1X X X X 1 0 0 0 1 0 0X X X X X 1 0 0 1 0 1X X X X X X 1 0 1 1 0X X X X X X X 1 1 1 1
I0 I1 I2 I3 I4 I5 I6 I7 Y2 Y1 Y0
Y0 = L7 # L5 # L3 # L1
L7 = I7L5 = !I7 & !I6 & I5L3 = !I7 & !I6 & !I5 & !I4 & I3L1 = !I7 & !I6 & !I5 & !I4 & !I3 & !I2 & I1
pencoder.ablMODULE pencoder83
TITLE 'Priority Encoder, A. Student, 7/15/02'
DECLARATIONS
" INPUT PINS "
I7..I0 PIN 6, 7, 11, 5, 72, 71, 66, 70; " Switch 1..8
" OUTPUT PINS "
Y2..Y0 PIN 37, 36, 35 ISTYPE 'com'; " LED 6..8
VALID PIN 44; " LED 1
" VALID = 1 for valid binary output
" INTERMEDIATE NODES "
L7..L0 NODE ISTYPE 'com'; " internal vector
pencoder.abl (cont’d)
EQUATIONS
L7 = I7;
L6 = !I7 & I6;
L5 = !I7 & !I6 & I5;
L4 = !I7 & !I6 & !I5 & I4;
L3 = !I7 & !I6 & !I5 & !I4 & I3;
L2 = !I7 & !I6 & !I5 & !I4 & !I3 & I2;
L1 = !I7 & !I6 & !I5 & !I4 & !I3 & !I2 & I1;
Y2 = L7 # L6 # L5 # L4;
Y1 = L7 # L6 # L3 # L2;
Y0 = L7 # L5 # L3 # L1;
END pencoder83
1 0 0 0 0 0 0 0 0 0 0X 1 0 0 0 0 0 0 0 0 1X X 1 0 0 0 0 0 0 1 0X X X 1 0 0 0 0 0 1 1X X X X 1 0 0 0 1 0 0X X X X X 1 0 0 1 0 1X X X X X X 1 0 1 1 0X X X X X X X 1 1 1 1
I0 I1 I2 I3 I4 I5 I6 I7 Y2 Y1 Y0
TTL Encoder
1
2
3
4
5
6
7
8 9
10
11
12
13
14
15
16
GND
Vcc
1
2
3
4 5
6
7
A2
A1
E1
E0
GS
0 A0
74LS148
1 X X X X X X X X 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 00 X X X X X X X 0 0 0 0 0 10 X X X X X X 0 1 0 0 1 0 10 X X X X X 0 1 1 0 1 0 0 10 X X X X 0 1 1 1 0 1 1 0 10 X X X 0 1 1 1 1 1 0 0 0 10 X X 0 1 1 1 1 1 1 0 1 0 1 0 X 0 1 1 1 1 1 1 1 1 0 0 10 0 1 1 1 1 1 1 1 1 1 1 0 1
EI 0 1 2 3 4 5 6 7 A2 A1 A0 GS EO
Priority Encoder
68000 Interrupt Logic
Peripheral
74148Encoder
74138Decoder
IP0IP1IP2
A0A1A2
IRQA
68000
Data Bus
IRQ
