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A strange problem with CMOS Up/Down counter

C

csl

Jan 1, 1970
0
Hey all,

Been searching for topics relating to what I have been experiencing and
to no avail.

Hopefully some of you might have a hint or tip. I am using a TI
CD40110B CMOS Up/Down decade counter. It has a separate clock up and
clock down. I connected to a Kingston 7-segment LED and here's what I
have been observing:

1. Counting up from 0 to 9 is ok.

2. Counting from 0 to 1 to 2 to 3 back to 2, when clock up is activated
nothing happens. When activated AGAIN, it jumps to 3.

3. Counting down from 9 to 2 to 3 then back to 2. Then clock up is
activated, nothing happens. When activated again, it jumps to 3.

I can't seem to figure out what's the problem. It only happens when one
returns from 3 to 2 and making an attempting back to 3.

If you have any suggestion, please post. Thanks for reading.
 
L

Luhan Monat

Jan 1, 1970
0
csl said:
Hey all,

Been searching for topics relating to what I have been experiencing and
to no avail.

Hopefully some of you might have a hint or tip. I am using a TI
CD40110B CMOS Up/Down decade counter. It has a separate clock up and
clock down. I connected to a Kingston 7-segment LED and here's what I
have been observing:

1. Counting up from 0 to 9 is ok.

2. Counting from 0 to 1 to 2 to 3 back to 2, when clock up is activated
nothing happens. When activated AGAIN, it jumps to 3.

3. Counting down from 9 to 2 to 3 then back to 2. Then clock up is
activated, nothing happens. When activated again, it jumps to 3.

I can't seem to figure out what's the problem. It only happens when one
returns from 3 to 2 and making an attempting back to 3.

If you have any suggestion, please post. Thanks for reading.

I would check the clock polarity. Make sure that the unused one is not
left in its active state when clocking.
 
L

Larry Brasfield

Jan 1, 1970
0
csl said:
Hey all, Yo.
Been searching for topics relating to what I have been experiencing and
to no avail.

Hopefully some of you might have a hint or tip. I am using a TI
CD40110B CMOS Up/Down decade counter. It has a separate clock up and
clock down. I connected to a Kingston 7-segment LED and here's what I
have been observing:

1. Counting up from 0 to 9 is ok.

2. Counting from 0 to 1 to 2 to 3 back to 2, when clock up is activated
nothing happens. When activated AGAIN, it jumps to 3.

3. Counting down from 9 to 2 to 3 then back to 2. Then clock up is
activated, nothing happens. When activated again, it jumps to 3.

I can't seem to figure out what's the problem. It only happens when one
returns from 3 to 2 and making an attempting back to 3.

If you have any suggestion, please post. Thanks for reading.

Something strikes me as odd about your description
that may help sort this out, (assuming Mr. Monat's
comments don't do it).

What is the difference between the count 2 to count 3
transition during your step 1 and what should be the
same transition during your step 2 or step 3? If the
problem is repeatable, there must be some difference
in conditions, either in the intended logic inputs or
in some unintended input arising from cabling, the
way the circuit is wired, interference, or ... something.
So, what is it? The answer will be telling.
 
A

Anthony Fremont

Jan 1, 1970
0
csl said:
I can't seem to figure out what's the problem. It only happens when one
returns from 3 to 2 and making an attempting back to 3.

If you have any suggestion, please post. Thanks for reading.

What are you using for the clock signal? If you have pull-ups on the
clock line, how big are they? I've had strange results like this when
the rise time was too slow on the clock.
 
C

csl

Jan 1, 1970
0
Thanks so much for the replies.

Luhan Monat: I checked the clock polarity. The "down" clock stays as it
should.

Larry Brasfield: Indeed, this observation is very perculiar. Yes,
problem is definitely repeatable. Somehow it appears to me that the IC
knows whether I am starting from 0 to 1 to 2 and so on. But whenever I
count from 3 to 2 and try to count back to 3, it won't allow me to do
so unless I double clock it. I tested everything. I checked everything.
Just doesn't make sense.

Anthony Fremont: I am using a tactile switch. I used a 10k resistor and
1uF capacitor. Thing is regardless of the size of the resistor or
capacitor, this problem is still there. But you brought up an
interesting point. So, if rise time is slow, it will take two "clicks"
to swich from 2 to 3 instead of one click? But why is it that it only
happens from 2 to 3?
 
C

csl

Jan 1, 1970
0
I want to add another observation...

Counting from 1 to 3 back to 2. At this point, if I click down to 1,
it's ok. Then count from 1 to 2 to 3. It's ok.
 
A

Anthony Fremont

Jan 1, 1970
0
csl said:
Anthony Fremont: I am using a tactile switch. I used a 10k resistor and
1uF capacitor. Thing is regardless of the size of the resistor or
capacitor, this problem is still there. But you brought up an
interesting point. So, if rise time is slow, it will take two "clicks"
to swich from 2 to 3 instead of one click? But why is it that it only
happens from 2 to 3?

My experience was with a serial shift register. Every thing worked good
until I clocked in a 0 bit, then all the outputs would reset
simultaneously. You could try using a Schmitt trigger inverter to
square up your clock signal and see if that helps.
 
C

csl

Jan 1, 1970
0
Anthony, thanks for the follow up.

I solved the issue this morning by adding a 0.15uF to the clock up
input and ground it. And now the "2 to 3" issue gone. Was there too
much noise?
 
B

Bob Monsen

Jan 1, 1970
0
Anthony said:
My experience was with a serial shift register. Every thing worked good
until I clocked in a 0 bit, then all the outputs would reset
simultaneously. You could try using a Schmitt trigger inverter to
square up your clock signal and see if that helps.

According to the TI datasheet, the maximum clock rise or fall time is
15us. Thus, your clock is far too slow. A 1uF cap + 10k resistor has a
tau of 1/100. That means it is about 1000 times too slow. There is some
wacky arbitration circuitry to protect against races between the clocks
which could be getting you.

Regards,
Bob Monsen
 
F

Fred Bloggs

Jan 1, 1970
0
Larry said:
Something strikes me as odd about your description
that may help sort this out, (assuming Mr. Monat's
comments don't do it).

What is the difference between the count 2 to count 3
transition during your step 1 and what should be the
same transition during your step 2 or step 3? If the
problem is repeatable, there must be some difference
in conditions, either in the intended logic inputs or
in some unintended input arising from cabling, the
way the circuit is wired, interference, or ... something.
So, what is it? The answer will be telling.

Unbelievable !!CRAP!! "What is it?"- that's what he's asking you,
stupid? And as usual, all anyone gets is a bunch of verbose gibberish.
If you don't know what you're doing then just stay the hell out of the
thread, you are a worthless jackass pseudo-intellectual.
 
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