Hex -to-ASCII Converter for your TVT-6

Hex-to-ASCII Converter for your

TVT-6

Simple module produces op-code display for entire computer.

BY DON LANCASTER

TH E LOW-COST "Hex-to-ASCII Converter" described here allows you to simultaneously display the con tents of every register, stack location,

and memory slot in your microcomputer.

The converter fits easily between the TVT-6 (July 1977) or most any other TVT and the ?C with which it is working.

OPCODE DATA FROM DISPLAY MEfilOR Y

V07

V06

V05

V04

I _;_j

I

V03

I

V02

:

VOi

I

VOfJ

-----,

OUTPUT T O T V T CHARACTER

GENERATOR

--- VD7

---vo&

V05

e:=--vD 4

V03

VD2

,__ _ _ VOi

'-v- o0

f-1.esEc-j

U/L u ' - ' -lf stP

I I I 1-f

L

u

-l l--0.1 SEC

L

u DISPLAY

Fig. 1. Block diagram of system. Op code is displayed as brief blank, followed by upper then lowe'I'. hex character.

OCTOBER 1977

In operation, the video monitor used in the system automatically converts and displays the hex op codes for the ASCII character set. This allows your TVT to act as a super "front panel" that permits you to check as many memory locations as there are in your system. This in cludes all registers, accumulator, stacks, RAM and ROM programs, 110, or anything else connected to the sys tem. Properly used, the converter is also an excellent debugging tool.

The complete hex-to-ASCII converter is built on a single compact printed cir cuit board. The circuit itself consists of three low-cost IC's and only five other parts.

About the Circuit. As shown in Fig. 1, the eight input lines from the display memory that normally drive the TVT character generator are intercepted and split into upper- and lower-case charac-

(Continued on page 51)

49

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I l . :i l ? ?

.,, 0 .,,

c:

:a m ... m n -4 :a 0 z

n

en

IORO

0

I

2

3 4 5 6

7 8

9 10

II

12

13 14

15 16

17 18

19 20

21

22 23 2'1

2

26

27 28 29

30 31

NOTES

Blank

11

" " "

817 716 615 51. 413

CJ CJ CJ CJ

I CJ c::; CJ CJ CJ

c::J CJ CJ CJ CJ

CJ D c CJ CJ CJ CJ CJ CJ CJ

11

CJ CJ CJ CJ CJ

11

CJ CJ CJ CJ CJ

If CJ CJ CJ CJ CJ

c: CJ CJ CJ CJ

11

c CJ CJ CJ CJ

"

CJ CJ CJ CJ CJ

11

CJ D CJ CJ CJ

CJ CJ D CJ CJ

"

CJ CJ D CJ CJ

"

CJ CJ CJ CJ CJ

II

CJ CJ CJ CJ CJ

0

CJ CJ CJ CJ 11"11!

1

- CJ CJ CJ -

2

c - D CJ -

3

- - CJ CJ -

4

CJ CJ - CJ ..

5

- CJ - CJ -

6

CJ - - Cl -

7

- - .. Cl lilt

8

Cl CJ CJ - ..

9

- c CJ - -

A

.. CJ CJ CJ CJ

B

CJ - CJ CJ CJ

c

.. - CJ Cl CJ

u

CJ CJ - CJ CJ

.t;

- CJ - CJ :::J

F

CJ - - CJ CJ

0-WHITE; 1-BLACK

312 211 110 - CJ c .. CJ CJ - CJ CJ - CJ CJ - CJ CJ - CJ CJ - CJ CJ - CJ CJ - CJ CJ - CJ CJ - CJ CJ - CJ CJ - CJ CJ .. CJ CJ - CJ CJ - CJ CJ - CJ CJ - CJ CJ

.. CJ CJ - CJ CJ - CJ CJ - CJ CJ - CJ CJ - CJ Cl - CJ CJ .. -C- J 0 CJ - CJ CJ - CJ Cl .. CJ CJ - CJ CJ - CJ

CJ '"' CJ

Fig. 3. Truth table for PROM IC2.

n +5V(SOURCEl C3

- l F

+5

-=-

[] ...- --- (36l+5V

OB0

OBI 082

SOI +5Vl36)

,

DB0

T

DBI

082

083

D83

OB4

DB4

DB5 OB6

DBS OB6

DB7

OB7 ,It

>-

Al

It

A2

0

A3

A4

:2

w

A5

:2

Al5 Al4

0.

Al3

:t_ Al2

Al

0

A2

1--

A3

1--

:2 V00

0

VOi

It V02

u. V03

1-- VD4

::>

VD5

0.

VD6

V07 z

-

w 0

CSI 0

16 8 15

-

8 15 16

Q3 9

-

10 A0

Q2 7

II Al

QI 4

12 A2

Q4 12

13 A3

ICI ? 74LS257 IC2 ?I M5610

'

0

0.

0

RI

I

4.7M

C2 .l1JF

1-::>

0.

0

R2 470K

0

VCL NC NC

=:! 1 NC

GND (l)GND

D

GND

VCL

NC NC NC

LGNO GNO(ll

Fig. 2. Oscillator IC3 is circuit timer for upper/lower display and interbyte pause.

i" ' rA ??oMi +sv

- .._l'l+ G. ?

IC2.

!

J

I

J I lf' "

I r=J .i. HEX.-sc11

J -----,, ,--47 _L_S 2 CONY1ERHR lI

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,]

J

I

?

IP

l(J ?s??

- (") -" . ? 8; :

N

t -J- -J

i- .U/l

!! =

g 0 8 0 0 V V UV

+P, 0 0 0 O q 0 0 ................
................

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