Elenco Electronics MO-1251 Manual do Utilizador descarregar pdf (Página 75)

P1

IC1

A

B

C

IC2

IC3

GND

4

11

10

9

6

7

8

2

14

16

FROM

PC5

PARALLEL

PORT

+V

B1

1.5V

+I

B2 1.5V

4+

B3

1.5V

I

16

11

10

9

6

7

8

ICI

4051

V

+V

16

3

IC2

4051

11

10

9

6

7

16

3

IC3

4051

13

14

15

12

5

2

4

13

14

15

12

1

5

2

4

13

14

15

12

1

5

2

4

J1 J1

1

2

3

4

5

6

7

9

10

It

12

13

14

15

16

17

18

19

20

21

22

23

24

25

2

3

4

5

6

7

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

13

14

15

12

1

5

2

4

13

14

15

12

1

5

2

4

13

14

15

12

IC4

4051

11

10

9

6

7

11

16

IC7-d

Y. 74C00

12

14I

13

IC5

4051

IC6

4051

11

10

9

6

16

3 V

11

10

9

3

V

-

IC8-a

7

x

40491

4

IC7-b

74C00 5

8

---

11

5

7

7

8

-±-

16V

IC7

a

4

74C00

2

Pl

X

Y

CO M

A

B

Fig. 4. COMPLETE SCHEMATIC DIAGRAM of the cable

tester.

The

circuitry to the left of

JI

is the

input side: to the

right

is the output. Plug PI connects to the PC's parallel port.

However,

we must be careful

not to disturb

bits D2, D1, and

DO,

which were previously

set.

We do that by reading

the status

of

port

888 and masking

off the

higher

bits

with

the function

INP(888) AND 7. That

gives us a

decimal value indicating

the sta-

tus of

bits D2 -DO. We can now

add the decimal value from bits

D7 -D3

to that number and send

it back

out. 'lb continue the pre-

vious example, we had

D7

=1,

D6 = 0, D5

=1, D4 = 0, and

D3 = 0, or 10100XXX

(with the X's

meaning

we don't care what

those bits are). The

decimal

number

for that pattern is

128x1 +64x0 +32x1 +16x

0+8x

0. or 160.

If

D2 =1, D1 =1, and D0 =0,

that pattern's

decimal equivalent

is 6. Add that to 160 and

we

get

166.

So to select

input line 15 and

output line

13. we

OUT

890,6

(to

select IC2), and OUT 888.166 (to

select transmission line 7 in IC2

and transmission line 5 in IC5).

Although the calculations

seem

somewhat involved, the

computer program accomplishes

them quickly; in Listing 1. see

lines 110 and 120 for the input

side and 250 -290 for the output

side of the PC Cable lbster.

Construction

1t"s

certainly

possible to design

a PC board for the tester, but

we

chose to build it on a standard

6

1/2-inch solderless

breadboard.

which provides just enough

room

for the circuit's eight IC's. Use

short lengths of

no. 22 solid wire

to make the breadboard

inter-

connections.

Next. obtain a

four -foot length

TABLE 1-4051 TRUTH TABLE

Inhibit A

B

C

Line

Selected

0 0

0 0

1

0 0 0

1

2

0 0 1

0 3

0 0 1 1 4

0 1

0 0 5

0 1

0

1

6

o 1 1

o

7

0

1 1

1

8

1

X X X

NONE

PARTS

LIST

IC1 -IC6

-4051, 8- channel CMOS

mux

demux

IC7- 74C00,

quad CMOS NAND

gate

IC8

-4049 quad

CMOS

hex inverter

R1- 10.000

ohms, ''..

watt,

5 °o

P1

-25

-pin D

Plug

and hood

J1,

J2

-25

-pin

D

socket and

hood

61/2-inch

x

2'/8 -inch solderless

breadboard

5

feet

of

15-

conductor, 24

AWG

un-

shielded cable

22

AWG

solid wire

2 -inch

. 6 -inch aluminum

panel

AA

battery

holder

(3 cells)

5 -inch 9 -inch

x

' /cinch plywood

base

3

AA

batteries

NOTE: An

enhanced

version

of

the

test program,

along with a de-

tailed description

of operation

is

available on a 51a

-inch

disk for

57.00

from

J. J.

Barbarello, RD

u3,

Box 241H, Tennent Road,

Manalapan, NJ

07726. Both

BASIC source and a compiled

version

of

the

program are

in-

cluded.

of 15- conductor cable: that cable

connects

to

the PC's printer port.

On

the

end that will attach to the

81

1 2 ... 70 71 72 73 74 75 76 77 78 79 80 ... 99 100

Comentários a estes Manuais

Sem comentários