Hi there, got a serious problem about Counters.
i have to create "a circuit that counts from 0 to 9 then from 9 to 0 using two separate counters" and "must consider BUS concept". i used two 74192 and two 74153 Multiplexers ( for BUS ), one of the counters is ascending and another one is descending.
i think i need some kind of SWITCH between these counters at the right time. so i did some works with those A and B pins on multiplexers, tried a few things:
* make it automatic using CLOCK (played with freq and period numbers).
* tried TRIBUFFER.
* LOAD pins.
** those 2 Logicstates down there should be automatic.
** 4 inputs for second counter are also for testing.
*** (as i said in the picture 9=>9=>8 or 9=>8 doesnt matter)
didnt work. can you please help?

 

hi P3301,
Welcome to AAC.
Are you saying that when the UP counter reaches a Count of '9', that a Bus transfer has to happen to Load the DOWN counter with '9', then the down counter counts to zero.?
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Update:
The circuit you have posted does not use the Bus concept.

 

hi P3301,
Welcome to AAC.
Are you saying that when the UP counter reaches a Count of '9', that a Bus transfer has to happen to Load the DOWN counter with '9', then the down counter counts to zero.?
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Update:
The circuit you have posted does not use the Bus concept.

Thank you!
exactly, 9 to 0 then 0 to 9 and again..
oh so what should i do? ( i moved to from 74192 to 74193 and both multiplexers to one 74157, seems better now, 92 start point and reset point was a little confusing)

 

hi P,
As this is homework I can only give you hints.
Look over this rough draft idea.
Complete the circuit and repost.

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hi P,
As this is homework I can only give you hints.
Look over this rough draft idea.
Complete the circuit and repost.

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i'm trying to complete it but the lower 74192 doesn't even count! it doesn't have any clock..
update: so i added a Clock to lower one, now both count in the opposite order to each other, but still the main problem is Switching from one counter to another.

 

hi,
You have to use logic gates to detect when the Up counter has reached a count of 9, then select the 157 IC.
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I see two problems on the 74157 multiplexer.

Inputs 1A, 2A, 3A, 4A should be wired to counter A.
Inputs 1B, 2B, 3B, 4B should be wired to counter B.

Pin-1 is your A/B input select.

 

hi,
It does not matter which way the 1A and 1B are used, providing the correct Select is set on the 74HC157.
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hi,
It does not matter which way the 1A and 1B are used, providing the correct Select is set on the 74HC157.
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ok i changed those A and B wires it seems the 7seg is showing the currect number now, i made that detect circuit still nothing. only for 1 second it switches to second counter and returns to first one, needs be on Descending IC for like 9-10 pulses :C
Is there anything that do this job in Proteus??

 

You need a flip-flop to implement "something" to hold the state of A/B select.

I would not consider a multiplexer to be implementation of a "bus concept".
You need a counter with output enable pin.

 

thank you guys.

 

hi P3301,
Note that on the 9th clock pulse into 74HC192, the TC/Up output pin goes Low and if not clocked again, remains Low.
Consider using that output to control the HC157 Select pin and the Up/Dwn clock control logic.
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solved it! by adding another counter, its clock is first counter's TCU and used its lowest value output to make that "something".

 

hi P,
That was a good solution,
Please post your final circuit so other will learn from your work.
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hey, sorry just checked my mailbox few minutes ago, here is the circuit:
all even numbers have 0 in the lowest value, and odd numbers have 1, i used this to control Multiplexer A/B pin