Code Converters

Section 3-4 Mano & Kime

Code Converters

• BCD-to Excess-3 Code Converter• Hex-to-Seven-Segment Decoder• Lab 3 – ALU2

– Arithmetic and Logic Instructions– 7-Segment Decoder

BCD-to Excess-3 Code Converter

Maps for BCD-to-Excess-3 Code Converter

Logic Diagram of BCD-to-Excess-3 Code Converter

Excess3inp(3:0) outp(3:0)

Note: inp(3:0) = [A, B, C, D] outp(3:0) = [W, X, Y, Z]

Code Converters

• BCD-to Excess-3 Code Converter• Hex-to-Seven-Segment Decoder• Lab 3 – ALU2

– Arithmetic and Logic Instructions– 7-Segment Decoder

Hex-to-Seven-Segment Decoder

a

b

c

d

e

f g

dp

a b c d e f g dp

q0

q1q2q3

seg7dec

Turning on an LED

+5V R LED

GAL output pin

+5V R LED

GAL output pin

1

0

+5V

+0.2V +1.7V

No current

Current light

no light

R = voltage current = 5 1.7

15 x 10 -3= 220 ohms

7-Segment Displaya

b

c

d

e

f g

a b c d e f g

+5V

7-Segment Displaya

b

c

d

e

f g

a b c d e f g0 1 1 1 1 1 1 01 0 1 1 0 0 0 02 1 1 0 1 1 0 13 1 1 1 1 0 0 14 0 1 1 0 0 1 15 1 0 1 1 0 1 16 1 0 1 1 1 1 17 1 1 1 0 0 0 0

7-Segment Displaya

b

c

d

e

f g

a b c d e f g8 1 1 1 1 1 1 19 1 1 1 1 0 1 1A 1 1 1 0 1 1 1b 0 0 1 1 1 1 1C 1 0 0 1 1 1 0d 0 1 1 1 1 0 1E 1 0 0 1 1 1 1F 1 0 0 0 1 1 1

a

b

c

d

e

f g

dp

a b c d e f g dp

q0

q1q2q3

seg7dec

Hex-to-Seven-Segment Decoder

a

b

c

d

e

f g

Note: a – g LOW to turn ON

Code Converters

• BCD-to Excess-3 Code Converter• Hex-to-Seven-Segment Decoder• Lab 3 – ALU2

– Arithmetic and Logic Instructions– 7-Segment Decoder

ALU2 – Arithmetic and Logic

Instructions a(n-1:0)

y(n-1:0)

sel(2:0)

n-lineALU2

b(n-1:0)

sel y Instruction name

“000” a + b +

“001” b - a -

“010” a and b AND

“011” a or b OR

“100” a xor b XOR

“101” true if a = 0false otherwise

0=

“110” true if a < 0false otherwise

0<

“111” true if b > a (unsigned)

false otherwise

U>

true = all 1’sfalse = all 0’s

Digilab2 – DIO1 Boards

Four 7-segmentdisplays

dig1 dig2 dig3 dig4

Digilab2 Board – Common Anodes

A1 A2 A3 A4

AtoG(6 downto 0)

Pins

Pins

switches

7-segment displays LEDs

pushbuttons

Digilab XLA

Digilab Board

dig3 dig2 dig1dig4

Digilab XLA Board – Common Anodes

A4 A3 A2 A1

CA CB CC CD CE CF CG

Pins

Pins

Top-level Design – Lab 3

a(3:0)ALU2

Lab3

sel(2:0)

ySW(5:8)

A(1:4)

BTN(1:3) ldg‘1’

SW(1:4) b(3:0)

AtoG(6:0)

seg7dec

q AtoG

“0001”

LD(1:8)

y1

Display yon dig4