# Hello, can you guide me with this BCD counter exercise?

#### Nao_Robot

Joined Jun 23, 2022
6
DESIGN USING IC 74193 (IN THE QUANTITY REQUIRED) AND COMBINATIONAL LOGIC TO DESIGN A BCD COUNTER FOR COUNTS 12 TO 75.

I managed to make it count from 12 to 75 but there are two details.

First
Once I start the simulation, I have to set the entries for the tens to one so that it counts from 12 to 75, because if it stays at 0 it only does this count:
12,13,14,15,16,17,18,19,10,11...19,10
Second, when the count reaches 75, on the next UP pulse it resets to 02 but not 12, and then counts: 02,03,04,05,06,07...75,02,03,04...

Tens Units
0 0 0 1 0 0 1 0 (12)
0 1 1 1 0 1 0 1 (75)

0 1 1 1 0 1 1 0 (76) --- (Which is where the ones of the tens are connected in the AND gate U6 )

What I wish is that when starting the simulation it counts from 12 to 75 without having to set the tens entries to one and once it reaches 75, it goes to 12 and counts again.

I am attaching the schematic of the circuit in PROTEUS (The units are on the counter on the left and the tens on the right).

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#### Ian0

Joined Aug 7, 2020
5,103
You have the wrong IC. 74193 is a binary counter.You need 74192 which is a BCD counter.
You seem to be using the reset on the tens, which will reset the tens to zero, when you should be using the parallel load and setting the D inputs to 0001.

#### Ramussons

Joined May 3, 2013
1,262
Why not make a simple counter that displays count from 12 and resets on 75? Whether one uses a Binary count or BCD will depend on the Display Driver. Or is the question something different?

#### Irving

Joined Jan 30, 2016
2,666
The original task, as stated by the TS, was:

" DESIGN USING IC 74193 (IN THE QUANTITY REQUIRED) AND COMBINATIONAL LOGIC TO DESIGN A BCD COUNTER FOR COUNTS 12 TO 75. "​

Using a 74192 is outside the task parameters, though it would simplify it a little.

So:
the units counter must count from 0 to 9, resetting to 0 when it gets to 10 ('BCD' logic) and additionally must be set to 2 on power on, and on the next clock after both counters reach 75;​
the tens counter must preset to 1 on power on, and on the next clock after the count gets to 75. It never goes above 7 so no 'BCD' logic is needed.​

#### Ian0

Joined Aug 7, 2020
5,103
The original task, as stated by the TS, was:

" DESIGN USING IC 74193 (IN THE QUANTITY REQUIRED) AND COMBINATIONAL LOGIC TO DESIGN A BCD COUNTER FOR COUNTS 12 TO 75. "​

Using a 74192 is outside the task parameters, though it would simplify it a little.
I do hate sisyphean assignments!

#### Irving

Joined Jan 30, 2016
2,666

#### dl324

Joined Mar 30, 2015
14,459
Welcome to AAC!
First
Once I start the simulation, I have to set the entries for the tens to one so that it counts from 12 to 75, because if it stays at 0 it only does this count:
12,13,14,15,16,17,18,19,10,11...19,10
That doesn't make sense. The LSD counter should increment to 10 and clock the MSD counter.
Second, when the count reaches 75, on the next UP pulse it resets to 02 but not 12, and then counts: 02,03,04,05,06,07...75,02,03,04...
You have the least significant bit input on the MSD counter floating.
I am attaching the schematic of the circuit in PROTEUS (The units are on the counter on the left and the tens on the right).
Why didn't you draw your schematic so the digits were in the correct order? I find it acceptable to not observe the typical schematic flow for counters and clocks.
1. Why do you have so many unnecessary wire jogs?
2. Why so much unnecessary whitespace?
3. Why do you have those 1/0 indicators on the displays when it appears that Proteus already indicates logic levels on all signals?
4. Why do you have U5A and U5B?
In the future, please print to PDF so we don't have to look at that awful grid and colored background.

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#### Nao_Robot

Joined Jun 23, 2022
6
You have the wrong IC. 74193 is a binary counter.You need 74192 which is a BCD counter.
You seem to be using the reset on the tens, which will reset the tens to zero, when you should be using the parallel load and setting the D inputs to 0001.
You have the wrong IC. 74193 is a binary counter.You need 74192 which is a BCD counter.
You seem to be using the reset on the tens, which will reset the tens to zero, when you should be using the parallel load and setting the D inputs to 0001.
You have the wrong IC. 74193 is a binary counter.You need 74192 which is a BCD counter.
You seem to be using the reset on the tens, which will reset the tens to zero, when you should be using the parallel load and setting the D inputs to 0001.
Yes I know, but in this case they ask me to use 74193.
That is, that the 74193 works as a BCD counter
I also thought that the error is in the tens because when it reaches 75 it goes to 02 when it should be 12
I'm going to check the connections on the tens anyway, thanks

#### Nao_Robot

Joined Jun 23, 2022
6
¿Por qué no hacer un contador simple que muestre la cuenta desde 12 y se reinicie en 75? El uso de un conteo binario o BCD dependerá del controlador de pantalla. ¿O la pregunta es algo diferente?
[/COTIZAR]
si eso es lo que quiero decir
Lo que pasa es que tengo que poner las entradas de las decenas a uno una vez que empieza la simulación para que funcione y cuando llega a 75 va a 02 y no a 12 que es lo que realmente quiero que haga, contar 12,13, 14,15....75 y de vuelta a 12 y así sucesivamente

#### Nao_Robot

Joined Jun 23, 2022
6
¡Bienvenido a CAA!
Eso no tiene sentido. El contador LSD debe incrementarse a 10 y sincronizar el contador MSD.
Tiene la entrada de bit menos significativa en el contador MSD flotante.
¿Por qué no dibujaste tu esquema para que los dígitos estuvieran en el orden correcto? Me parece aceptable no observar el típico flujo esquemático de contadores y relojes.
1. ¿Por qué tienes tantos cambios de cables innecesarios?
2. ¿Por qué tanto espacio en blanco innecesario?
3. ¿Por qué tiene esos indicadores 1/0 en las pantallas cuando parece que Proteus ya indica niveles lógicos en todas las señales?
4. ¿Por qué tienes U5A y U5B?
En el futuro, imprima en PDF para que no tengamos que mirar esa cuadrícula horrible y el fondo de color.
[/COTIZAR]
Soy nuevo en esto, los NOTS U5A y U5B son para que aprecies la cuenta, porque entiendo que si no los usas, corre muy rápido.
Lo tendré en cuenta de todos modos, gracias.

#### dl324

Joined Mar 30, 2015
14,459
Soy nuevo en esto, los NOTS U5A y U5B son para que aprecies la cuenta, porque entiendo que si no los usas, corre muy rápido.
Lo tendré en cuenta de todos modos, gracias.

Translation:
"I'm new to this, the U5A and U5B NOTS are for you to appreciate the bill, because I understand that if you don't use them, run very fast.
I'll keep that in mind anyway, thank you."

The counters are synchronous, so you shouldn't have any problems with race conditions.

Take a look at the reset and preset on the 10's counter. It's wrong.

This is how I drew the solution to your problem (with the answer covered):

The symbol used by Proteus isn't conducive to this layout, but you can create your own.

The simulator I use had no useful commercial parts, so I created my own. Since 74193/74LS193 counters are up/down, it makes sense to arrange the borrow and carry inputs/outputs to facilitate cascading them.

Since your new, note that I mixed TTL with CMOS. The simulator doesn't care, but in real circuits, it's not a good idea because TTL outputs aren't guaranteed to drive CMOS inputs.

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#### Nao_Robot

Joined Jun 23, 2022
6
It's good to know that 74193 can be counted up and down
Cheers

#### dl324

Joined Mar 30, 2015
14,459
It's good to know that 74193 can be counted up and down
Did you find the problems with your logic for the 10's counter?

#### dl324

Joined Mar 30, 2015
14,459
I just noticed that the clock inputs for my LS193 component shouldn't have bubbles as they're HIGH active. It doesn't affect the functionality of the counter I made.