Parallel Interfacing

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Parallel Interfacing

• Chapter 7

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Parallel Interfacing

• Parallel I/O Ports
• Using Parallel Ports
• Seven-Segment Displays
• Keypad Interfacing
• Liquid Crystal Displays
• Interrupt-Driven Traffic Lights

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Port and Data Direction Registers
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MC68HC711E9
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PORTA
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Parallel Interfacing

• Parallel I/O Ports
• Using Parallel Ports
• Seven-Segment Displays
• Keypad Interfacing
• Liquid Crystal Displays
• Interrupt-Driven Traffic Lights

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Turning on an LED
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Using an AC Relay
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Interfacing a switch input
HEX F0 DDRH C! ?open ( -- f ) 2 PORTH
?HI
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Parallel Interfacing

• Parallel I/O Ports
• Using Parallel Ports
• Seven-Segment Displays
• Keypad Interfacing
• Liquid Crystal Displays
• Interrupt-Driven Traffic Lights

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Common Anode 7-Segment Display
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Interfacing a 7-Segment Display
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Common-Cathode Displays The MC14495-1
7 6 5 4 3 2
1 0
2 digits PORTH 0 0 LE1 LE0 D C B A
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Parallel Interfacing

• Parallel I/O Ports
• Using Parallel Ports
• Seven-Segment Displays
• Keypad Interfacing
• Liquid Crystal Displays
• Interrupt-Driven Traffic Lights

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4 x 4 Hex Keypad
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Registers associated with parallel I/O on Port J
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Scanning a 4 x 4 keypad
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Scanning a 4 x 4 keypad

keypad ( -- n )
BEGIN

?keypad

UNTIL
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Axiom Keypad
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Axiom 4 x 4 Hex Keypad
1
2
3
4
Row
Col
1
2
3
A
1K
4
PH0
4
5
6
B
3
PH1
7
8
9
C
2
PH2

0

D
1
PH3
PH4
PH5
PH6
PH7
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Debounce
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Displaying keys pressed on a 7-segment display

keypad ( -- n )
BEGIN

?keypad

UNTIL

wait.for.keyup ( -- )
BEGIN

?keypad
WHILE
DROP

REPEAT

main.keypad ( -- )

init.key
BEGIN

keypad

.led

wait.for.keyup

AGAIN
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Including debounce when reading a keypad
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The 74C922 16-Key Encoder
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Reading a keypad using the 74C922 16-Key Encoder
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Interfacing a 16 x 1 hex keypad to a
68HC711E9 using a 74154
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Scanning a 16 x 1 keypad
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Parallel Interfacing

• Parallel I/O Ports
• Using Parallel Ports
• Seven-Segment Displays
• Keypad Interfacing
• Liquid Crystal Displays
• Interrupt-Driven Traffic Lights

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Liquid Crystal Display
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Relationship between RS, R/W, and E
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Axiom LCD
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Parallel Interfacing

• Parallel I/O Ports
• Using Parallel Ports
• Seven-Segment Displays
• Keypad Interfacing
• Liquid Crystal Displays
• Interrupt-Driven Traffic Lights

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Traffic Lights Using Real-time Interrupt
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Traffic Lights Using Real-time Interrupt
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Traffic Lights Using Real-time Interrupt
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