Counter ICs

[Richard]

MC14017B

http://www.onsemi.com/pub_link/Collateral/MC14017B-D.PDF

I've just begun to look at digital electronics, and of course I have
come across the 4 bit counter.

In a 4 bit counter the output is at Q1, Q2, Q3 and Q4. We can feed these
4 bits (from a decade counter usually) into a decoder to drive a 7
segment display.

MC14017B is a 5 stage counter with built in code converter and shows
outputs Q0 - Q9.

Is this actually like a 5 bit counter, or what? Thanks.

 

[Jon Kirwan]

On Thu, 30 Jun 2011 10:29:37 +0100, Richard
<none@ntlworld.com> wrote:

MC14017B

http://www.onsemi.com/pub_link/Collateral/MC14017B-D.PDF

I've just begun to look at digital electronics, and of course I have
come across the 4 bit counter.

In a 4 bit counter the output is at Q1, Q2, Q3 and Q4. We can feed these
4 bits (from a decade counter usually) into a decoder to drive a 7
segment display.

MC14017B is a 5 stage counter with built in code converter and shows
outputs Q0 - Q9.

Is this actually like a 5 bit counter, or what? Thanks.

Examine this java-coded display of one:

http://www.falstad.com/circuit/e-johnsonctr.html

It's a 5-bit ring, but the output of the last bit is inverted
and fed back so it takes two loops through to repeat itself
completely.

Jon

 

[Jasen Betts]

On 2011-06-30, Richard <none@ntlworld.com> wrote:

MC14017B

http://www.onsemi.com/pub_link/Collateral/MC14017B-D.PDF

I've just begun to look at digital electronics, and of course I have
come across the 4 bit counter.

Hi, you've found a data-sheet that's a really good start.

MC14017B is a 5 stage counter with built in code converter and shows
outputs Q0 - Q9.

Is this actually like a 5 bit counter, or what? Thanks.

actually it's a 5 bit shift register fed back it's inverted output
then run through a bunch of gates (see page 2 of the data sheet)

it counts to 10 having one output (Q0-Q9) high for each step.

It's basically the same chip as the 4017B used here.

http://www.technologystudent.com/elec1/count1.htm

not that I'm reccomend that circuit (with a 9V supply) other than as an
experiment as it's using the LEDS outside of their specifications and
they may not last very long, it's better to use one resistor for each LED

--
⚂⚃ 100% natural

 

[Richard]

On 30/06/2011 12:30, Jasen Betts wrote:

On 2011-06-30, Richard<none@ntlworld.com> wrote:
MC14017B

http://www.onsemi.com/pub_link/Collateral/MC14017B-D.PDF

I've just begun to look at digital electronics, and of course I have
come across the 4 bit counter.

Hi, you've found a data-sheet that's a really good start.

MC14017B is a 5 stage counter with built in code converter and shows
outputs Q0 - Q9.

Is this actually like a 5 bit counter, or what? Thanks.

actually it's a 5 bit shift register fed back it's inverted output
then run through a bunch of gates (see page 2 of the data sheet)

it counts to 10 having one output (Q0-Q9) high for each step.

It's basically the same chip as the 4017B used here.

http://www.technologystudent.com/elec1/count1.htm

not that I'm reccomend that circuit (with a 9V supply) other than as an
experiment as it's using the LEDS outside of their specifications and
they may not last very long, it's better to use one resistor for each LED

Hi. So it's not a 4 digit counter, it's 10 digit counter, and that is
why we see Q0 -Q9. But there is a 5 shift register in the IC.

Not sure what the code converter is about though.

At present what interests me is a decade counter.

From what I read, for each 7 segment display, you require 4 bits
representing the count, and you are getting Binary Coded Decimal at
Q1-Q4 (because we are using decade counters) and not regular binary
(modulo 16?). So, when building for 7 segment displays you need 4 bits
for every display. Therefore you would need a 16 bit counter (4 x 4 bit)
to run four 7 segment LED displays. I guess so.

 

[Richard]

On 30/06/2011 12:50, Richard wrote:

Hi. So it's not a 4 digit counter, it's 10 digit counter, and that is
why we see Q0 -Q9. But there is a 5 shift register in the IC.

I mean 4 bit and 10 bit.

 

[Richard]

On 30/06/2011 11:58, Jon Kirwan wrote:

On Thu, 30 Jun 2011 10:29:37 +0100, Richard
none@ntlworld.com> wrote:

MC14017B

http://www.onsemi.com/pub_link/Collateral/MC14017B-D.PDF

I've just begun to look at digital electronics, and of course I have
come across the 4 bit counter.

In a 4 bit counter the output is at Q1, Q2, Q3 and Q4. We can feed these
4 bits (from a decade counter usually) into a decoder to drive a 7
segment display.

MC14017B is a 5 stage counter with built in code converter and shows
outputs Q0 - Q9.

Is this actually like a 5 bit counter, or what? Thanks.

Examine this java-coded display of one:

http://www.falstad.com/circuit/e-johnsonctr.html

It's a 5-bit ring, but the output of the last bit is inverted
and fed back so it takes two loops through to repeat itself
completely.

Jon

I've not enough knowledge yet to understand these counter IC's.

I've just started learning digital, and all I know about is 4 bit
counters and how you can use those 4 bits (BCD in a decade counter) to
run a 7 segment display (via a BCD decoder).

So, when I think about counters with 7 segment displays, I'm assuming
your counter must be 4 bit, 8 bit, 12 bit etc.

I think this is true except for ring counters.

I just don't know why, with a decade counter, there are 10 bits in the
IC MC14017B-D and not multiples of 4bits.

 

[Josef Moellers]

Am 30.6.2011 schrub Richard:

MC14017B

http://www.onsemi.com/pub_link/Collateral/MC14017B-D.PDF

I've just begun to look at digital electronics, and of course I have
come across the 4 bit counter.

In a 4 bit counter the output is at Q1, Q2, Q3 and Q4. We can feed these
4 bits (from a decade counter usually) into a decoder to drive a 7
segment display.

MC14017B is a 5 stage counter with built in code converter and shows
outputs Q0 - Q9.

Is this actually like a 5 bit counter, or what? Thanks.

They just use different codes:
the 4 bit counter outputs a base-2 code while the 10 bit counter outputs
a 1-out-of-10 code:

base-2 1-out-of-10
0000 0000000001
0001 0000000010
0010 0000000100
0011 0000001000
0100 0000010000
0101 0000100000
0110 0001000000
0111 0010000000
1000 0100000000
1001 1000000000

The 1-out-of-10 counter could just as well be implemented using a base-2
BCD counter (e.g. an SN74LS160A) and a decoder (e.g. an SN74LS145).

Josef
--
These are my personal views and not those of Fujitsu Technology Solutions!
Josef Möllers (Pinguinpfleger bei FTS)
If failure had no penalty success would not be a prize (T. Pratchett)
Company Details: http://de.ts.fujitsu.com/imprint.html

 

[Josef Moellers]

Am 30.6.2011 schrub Richard:

On 30/06/2011 11:58, Jon Kirwan wrote:
On Thu, 30 Jun 2011 10:29:37 +0100, Richard
none@ntlworld.com> wrote:

MC14017B

http://www.onsemi.com/pub_link/Collateral/MC14017B-D.PDF

I've just begun to look at digital electronics, and of course I have
come across the 4 bit counter.

In a 4 bit counter the output is at Q1, Q2, Q3 and Q4. We can feed these
4 bits (from a decade counter usually) into a decoder to drive a 7
segment display.

MC14017B is a 5 stage counter with built in code converter and shows
outputs Q0 - Q9.

Is this actually like a 5 bit counter, or what? Thanks.

Examine this java-coded display of one:

http://www.falstad.com/circuit/e-johnsonctr.html

It's a 5-bit ring, but the output of the last bit is inverted
and fed back so it takes two loops through to repeat itself
completely.

Jon

I've not enough knowledge yet to understand these counter IC's.

I've just started learning digital, and all I know about is 4 bit
counters and how you can use those 4 bits (BCD in a decade counter) to
run a 7 segment display (via a BCD decoder).

It must be a decoder which outputs a special code, as a simple "BCD
decoder" will output a 1-out-of-10 code. What you need is one that
outputs a code geared towards 7-segment displays:

Input Output
0000 1110111
0001 0100100
0010 1011101
0011 1101101
0100 0101110
0101 1101011
0110 1111011
0111 0100101
1000 1111111
1001 1101111

The least significant bit of the output is the top horizontal bar, then
the more significant bits are arranged from top to bottom and from left
to right:
0
+-----+
| |
|1 |2
| 3 |
+-----+
| |
|4 |5
| 6 |
+-----+

Take a look at e.g. the 4511, the 7447 or any other "BCD to 7-segment
decoder/driver".

So, when I think about counters with 7 segment displays, I'm assuming
your counter must be 4 bit, 8 bit, 12 bit etc.

It depends upon your display. You might want to count in octal, then a
number of 3-bit counters is sufficient ;-)

Note that the integrated decodes/drivers also have a feature to suppress
leading 0s.

I think this is true except for ring counters.

I just don't know why, with a decade counter, there are 10 bits in the
IC MC14017B-D and not multiples of 4bits.

Because the code it outputs is a 1-of-10 code.

Josef
--
These are my personal views and not those of Fujitsu Technology Solutions!
Josef Möllers (Pinguinpfleger bei FTS)
If failure had no penalty success would not be a prize (T. Pratchett)
Company Details: http://de.ts.fujitsu.com/imprint.html

 

[Richard]

On 30/06/2011 13:19, Josef Moellers wrote:

Am 30.6.2011 schrub Richard:

MC14017B

http://www.onsemi.com/pub_link/Collateral/MC14017B-D.PDF

I've just begun to look at digital electronics, and of course I have
come across the 4 bit counter.

In a 4 bit counter the output is at Q1, Q2, Q3 and Q4. We can feed these
4 bits (from a decade counter usually) into a decoder to drive a 7
segment display.

MC14017B is a 5 stage counter with built in code converter and shows
outputs Q0 - Q9.

Is this actually like a 5 bit counter, or what? Thanks.

They just use different codes:
the 4 bit counter outputs a base-2 code while the 10 bit counter outputs
a 1-out-of-10 code:

base-2 1-out-of-10
0000 0000000001
0001 0000000010
0010 0000000100
0011 0000001000
0100 0000010000
0101 0000100000
0110 0001000000
0111 0010000000
1000 0100000000
1001 1000000000

The 1-out-of-10 counter could just as well be implemented using a base-2
BCD counter (e.g. an SN74LS160A) and a decoder (e.g. an SN74LS145).

Josef

Hi. Yes, the 4 bit counters that I am reading about are all binary
counters. Even the decade (BCD) counter is, except that BCD in the whole
sequence of bits are not binary.

And in this scheme I see how each display LED requires a Q1-Q4 output
from a 4 bit counter.

So to display a count of 7953 we need four, 4 bit counters:


Q1-Q4 Q1-Q4 Q1-Q4 Q1-Q4
BCD sequence:......... 0111 1001 0101 0011

Decimal displayed:.......... 7 9 5 3

Output of 4 bit counter is base-2 code.

Not sure yet how you would get to display 7953 using the 10 bit counter.
Whether in fact you would or could use 7 segment LED displays.

 

[John Fields]

On 30 Jun 2011 11:30:26 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:

On 2011-06-30, Richard <none@ntlworld.com> wrote:
MC14017B

http://www.onsemi.com/pub_link/Collateral/MC14017B-D.PDF

I've just begun to look at digital electronics, and of course I have
come across the 4 bit counter.

Hi, you've found a data-sheet that's a really good start.

MC14017B is a 5 stage counter with built in code converter and shows
outputs Q0 - Q9.

Is this actually like a 5 bit counter, or what? Thanks.

actually it's a 5 bit shift register fed back it's inverted output
then run through a bunch of gates (see page 2 of the data sheet)

---
It's actually a 5 stage Johnson counter; a shift register is quite a
different animal.
---

it counts to 10 having one output (Q0-Q9) high for each step.

It's basically the same chip as the 4017B used here.

http://www.technologystudent.com/elec1/count1.htm

not that I'm reccomend that circuit (with a 9V supply) other than as an
experiment as it's using the LEDS outside of their specifications and
they may not last very long, it's better to use one resistor for each LED

---
How so?

Since there's never more than one LED ON at time, a single resistor is
fine.

--
JF

 

[John Fields]

On Thu, 30 Jun 2011 10:29:37 +0100, Richard <none@ntlworld.com> wrote:

MC14017B

http://www.onsemi.com/pub_link/Collateral/MC14017B-D.PDF

I've just begun to look at digital electronics, and of course I have
come across the 4 bit counter.

In a 4 bit counter the output is at Q1, Q2, Q3 and Q4. We can feed these
4 bits (from a decade counter usually) into a decoder to drive a 7
segment display.

MC14017B is a 5 stage counter with built in code converter and shows
outputs Q0 - Q9.

Is this actually like a 5 bit counter, or what? Thanks.

---
It's actually more like a tricky 4 bit counter which only uses 10 of
the possible 16 output steps and presents them on the outputs one at a
time.

--
JF

 

[Richard]

So to display a count of 7953 we need four, 4 bit counters:

........................ Q1-Q4 Q1-Q4 Q1-Q4 Q1-Q4
BCD sequence:.......... 0111 1001 0101 0011

Decimal displayed:..... 7 9 5 3
(on 7 segment LED)

Output of 4 bit counter is base-2 code.
---

Basically, how would you complete the above arrangement for this 10 bit
counter:

........................ Q0 Q1 Q2 Q3 Q$ Q5 Q6 Q7 Q8 Q9

??? sequence:..........

Decimal displayed:..... 7 9 5 3
(on 7 segment LED)

 

[Richard]

So to display a count of 7953 we need four, 4 bit counters:

........................ Q1-Q4 Q1-Q4 Q1-Q4 Q1-Q4
BCD sequence:.......... 0111 1001 0101 0011

BCD decoder (to drive LED driver)

Decimal displayed:..... 7 9 5 3
(on four 7 segment LEDs)

Output of each 4 bit counter is base-2 code.
---

Basically, how would you make out a similar arrangement to the above for
the 10 bit counter? What would it take to display 7953 on four seven
segment display LEDs? How many counters?

........................ Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

??? sequence:..........

??? decoder:..........


Decimal displayed:..... 7 9 5 3
(on four 7 segment LEDs)

 

[Richard]

On 30/06/2011 14:23, Richard wrote:

So to display a count of 7953 we need four, 4 bit counters:

....................... Q1-Q4 Q1-Q4 Q1-Q4 Q1-Q4
BCD sequence:.......... 0111 1001 0101 0011

BCD decoder (to drive LED driver)

Decimal displayed:..... 7 9 5 3
(on four 7 segment LEDs)

Output of each 4 bit counter is base-2 code.
---

Basically, how would you make out a similar arrangement to the above for
the 10 bit counter? What would it take to display 7953 on four seven
segment display LEDs? How many counters?

....................... Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

??? sequence:..........

??? decoder:..........


Decimal displayed:..... 7 9 5 3
(on four 7 segment LEDs)

Are we saying for 10 bit counter when the count reaches 7953 we have:

........................ Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

1 in 10 sequence:...... X X X X

X = HIGH

1 in 10 decoder: (To drive LED driver)


Decimal displayed:..... 7 9 5 3
(on four 7 segment LEDs)

 

[John Fields]

On Thu, 30 Jun 2011 12:50:51 +0100, Richard <none@ntlworld.com> wrote:

On 30/06/2011 12:30, Jasen Betts wrote:

On 2011-06-30, Richard<none@ntlworld.com> wrote:
MC14017B

http://www.onsemi.com/pub_link/Collateral/MC14017B-D.PDF

I've just begun to look at digital electronics, and of course I have
come across the 4 bit counter.

Hi, you've found a data-sheet that's a really good start.

MC14017B is a 5 stage counter with built in code converter and shows
outputs Q0 - Q9.

Is this actually like a 5 bit counter, or what? Thanks.

actually it's a 5 bit shift register fed back it's inverted output
then run through a bunch of gates (see page 2 of the data sheet)

it counts to 10 having one output (Q0-Q9) high for each step.

It's basically the same chip as the 4017B used here.

http://www.technologystudent.com/elec1/count1.htm

not that I'm reccomend that circuit (with a 9V supply) other than as an
experiment as it's using the LEDS outside of their specifications and
they may not last very long, it's better to use one resistor for each LED

Hi. So it's not a 4 digit counter, it's 10 digit counter, and that is
why we see Q0 -Q9. But there is a 5 shift register in the IC.

Not sure what the code converter is about though.

At present what interests me is a decade counter.

From what I read, for each 7 segment display, you require 4 bits
representing the count, and you are getting Binary Coded Decimal at
Q1-Q4 (because we are using decade counters) and not regular binary
(modulo 16?). So, when building for 7 segment displays you need 4 bits
for every display. Therefore you would need a 16 bit counter (4 x 4 bit)
to run four 7 segment LED displays. I guess so.

---
Almost.

Here's the difference between the counting patterns of decade and
binary counters outputs:

CLOCK DECADE BINARY
0UT OUT

0 0000 0000
1 0001 0001
2 0010 0010
3 0011 0011
4 0100 0100
5 0101 0101
6 0110 0110
7 0111 0111
8 1000 1000
9 1001 1001
10 0000 <- 1010
11 0001 1011
12 0010 1100
13 0011 1101
14 0100 1110
15 0101 1111
16 0110 0000 <-

Notice that the decade counter overflows at the 10th clock, while the
binary counter overflows at the 16th.

That means that if a binary counter is used to drive a BCD to
7-segment decoder, the decoder won't display anything between 1001 and
0000.

So, the most rudimentary way to drive 4, 7 segment displays would be
to use 4, 4 bit BCD counters, 4 BCD to 7 segment displays, and 4,
7-segment displays.

--
JF

 

[John Fields]

On Thu, 30 Jun 2011 13:43:08 +0100, Richard <none@ntlworld.com> wrote:

On 30/06/2011 13:19, Josef Moellers wrote:
Am 30.6.2011 schrub Richard:

MC14017B

http://www.onsemi.com/pub_link/Collateral/MC14017B-D.PDF

I've just begun to look at digital electronics, and of course I have
come across the 4 bit counter.

In a 4 bit counter the output is at Q1, Q2, Q3 and Q4. We can feed these
4 bits (from a decade counter usually) into a decoder to drive a 7
segment display.

MC14017B is a 5 stage counter with built in code converter and shows
outputs Q0 - Q9.

Is this actually like a 5 bit counter, or what? Thanks.

They just use different codes:
the 4 bit counter outputs a base-2 code while the 10 bit counter outputs
a 1-out-of-10 code:

base-2 1-out-of-10
0000 0000000001
0001 0000000010
0010 0000000100
0011 0000001000
0100 0000010000
0101 0000100000
0110 0001000000
0111 0010000000
1000 0100000000
1001 1000000000

The 1-out-of-10 counter could just as well be implemented using a base-2
BCD counter (e.g. an SN74LS160A) and a decoder (e.g. an SN74LS145).

Josef

Hi. Yes, the 4 bit counters that I am reading about are all binary
counters. Even the decade (BCD) counter is, except that BCD in the whole
sequence of bits are not binary.

And in this scheme I see how each display LED requires a Q1-Q4 output
from a 4 bit counter.

So to display a count of 7953 we need four, 4 bit counters:


Q1-Q4 Q1-Q4 Q1-Q4 Q1-Q4
BCD sequence:......... 0111 1001 0101 0011

Decimal displayed:.......... 7 9 5 3

Output of 4 bit counter is base-2 code.

Not sure yet how you would get to display 7953 using the 10 bit counter.

Whether in fact you would or could use 7 segment LED displays.

---
You could, but you'd have to use a one out of ten to 7 segment
decoder.

Unobtainium, I think, unless you rolled your own.

--
JF

 

[John Fields]

On Thu, 30 Jun 2011 14:14:10 +0100, Richard <none@ntlworld.com> wrote:

So to display a count of 7953 we need four, 4 bit counters:

....................... Q1-Q4 Q1-Q4 Q1-Q4 Q1-Q4
BCD sequence:.......... 0111 1001 0101 0011

Decimal displayed:..... 7 9 5 3
(on 7 segment LED)

Output of 4 bit counter is base-2 code.
---

Basically, how would you complete the above arrangement for this 10 bit
counter:

....................... Q0 Q1 Q2 Q3 Q$ Q5 Q6 Q7 Q8 Q9

??? sequence:..........

Decimal displayed:..... 7 9 5 3
(on 7 segment LED)

---
That won't work; you'd have to use four 4017's and four "one out of
ten to 7 segment decoders".

--
JF

 

[Josef Moellers]

Am 30.6.2011 schrub Richard:

On 30/06/2011 13:19, Josef Moellers wrote:
Am 30.6.2011 schrub Richard:

MC14017B

http://www.onsemi.com/pub_link/Collateral/MC14017B-D.PDF

I've just begun to look at digital electronics, and of course I have
come across the 4 bit counter.

In a 4 bit counter the output is at Q1, Q2, Q3 and Q4. We can feed these
4 bits (from a decade counter usually) into a decoder to drive a 7
segment display.

MC14017B is a 5 stage counter with built in code converter and shows
outputs Q0 - Q9.

Is this actually like a 5 bit counter, or what? Thanks.

They just use different codes:
the 4 bit counter outputs a base-2 code while the 10 bit counter outputs
a 1-out-of-10 code:

base-2 1-out-of-10
0000 0000000001
0001 0000000010
0010 0000000100
0011 0000001000
0100 0000010000
0101 0000100000
0110 0001000000
0111 0010000000
1000 0100000000
1001 1000000000

The 1-out-of-10 counter could just as well be implemented using a base-2
BCD counter (e.g. an SN74LS160A) and a decoder (e.g. an SN74LS145).

Josef

Hi. Yes, the 4 bit counters that I am reading about are all binary
counters. Even the decade (BCD) counter is, except that BCD in the whole
sequence of bits are not binary.

And in this scheme I see how each display LED requires a Q1-Q4 output
from a 4 bit counter.

So to display a count of 7953 we need four, 4 bit counters:


Q1-Q4 Q1-Q4 Q1-Q4 Q1-Q4
BCD sequence:......... 0111 1001 0101 0011

Decimal displayed:.......... 7 9 5 3

Output of 4 bit counter is base-2 code.

Not sure yet how you would get to display 7953 using the 10 bit counter.
Whether in fact you would or could use 7 segment LED displays.

Without some additional circuitry: you can't!
The 1-of-10 code does not directly map to the 7 segments. You'd need a
couple of OR gates:
Segment 0 (the top most bar) is on if
Q0 OR Q2 OR Q3 OR Q5 OR Q6 OR Q7 OR Q8 OR Q9
is on
....

The BCD to 7-segment decode/driver chips use a slightly more complex
logic to determine which combination of the 4 bits causes which segment
to light.
It would be a nice exercise for Karnaugh-Veitch (sp?) diagrams!

Josef


--
These are my personal views and not those of Fujitsu Technology Solutions!
Josef Möllers (Pinguinpfleger bei FTS)
If failure had no penalty success would not be a prize (T. Pratchett)
Company Details: http://de.ts.fujitsu.com/imprint.html

 

[John Fields]

On Thu, 30 Jun 2011 14:40:51 +0100, Richard <none@ntlworld.com> wrote:

On 30/06/2011 14:23, Richard wrote:
So to display a count of 7953 we need four, 4 bit counters:

....................... Q1-Q4 Q1-Q4 Q1-Q4 Q1-Q4
BCD sequence:.......... 0111 1001 0101 0011

BCD decoder (to drive LED driver)

Decimal displayed:..... 7 9 5 3
(on four 7 segment LEDs)

Output of each 4 bit counter is base-2 code.
---

Basically, how would you make out a similar arrangement to the above for
the 10 bit counter? What would it take to display 7953 on four seven
segment display LEDs? How many counters?

....................... Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

??? sequence:..........

??? decoder:..........


Decimal displayed:..... 7 9 5 3
(on four 7 segment LEDs)

Are we saying for 10 bit counter when the count reaches 7953 we have:

....................... Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

1 in 10 sequence:...... X X X X

X = HIGH

1 in 10 decoder: (To drive LED driver)


Decimal displayed:..... 7 9 5 3
(on four 7 segment LEDs)

---
Here: (View in Courier)

.. DIGIT 4
.. COUNT DECODE DISPLAY
.. +-----+ +------+ +-----+
.. | Q9|---|IN9 g|---|g |
.. . . . . . .
.. . . . . . .
.. . . . . . .
.. | Q0|---|IN0 a|---|a |
.. +-----+ +------+ +-----+
..
.. DIGIT 3
.. COUNT DECODE DISPLAY
.. +-----+ +------+ +-----+
.. | Q9|---|IN9 g|---|g |
.. . . . . . .
.. . . . . . .
.. . . . . . .
.. | Q0|---|IN0 a|---|a |
.. +-----+ +------+ +-----+
..
.. DIGIT 2
.. COUNT DECODE DISPLAY
.. +-----+ +------+ +-----+
.. | Q9|---|IN9 g|---|g |
.. . . . . . .
.. . . . . . .
.. . . . . . .
.. | Q0|---|IN0 a|---|a |
.. +-----+ +------+ +-----+
..
.. DIGIT 1
.. COUNT DECODE DISPLAY
.. +-----+ +------+ +-----+
.. | Q9|---|IN9 g|---|g |
.. . . . . . .
.. . . . . . .
.. . . . . . .
.. | Q0|---|IN0 a|---|a |
.. +-----+ +------+ +-----+

The clocks into and the carries into/out of the counters aren't shown,
but what happens is that as the count sequence progresses, the outputs
which are hot get decoded so that the LED segments corresponding to
the numerical values of those hot outputs are illuminated.

--
JF

 

[Richard]

On 30/06/2011 15:31, John Fields wrote:

On Thu, 30 Jun 2011 14:40:51 +0100, Richard<none@ntlworld.com> wrote:

On 30/06/2011 14:23, Richard wrote:
So to display a count of 7953 we need four, 4 bit counters:

....................... Q1-Q4 Q1-Q4 Q1-Q4 Q1-Q4
BCD sequence:.......... 0111 1001 0101 0011

BCD decoder (to drive LED driver)

Decimal displayed:..... 7 9 5 3
(on four 7 segment LEDs)

Output of each 4 bit counter is base-2 code.
---

Basically, how would you make out a similar arrangement to the above for
the 10 bit counter? What would it take to display 7953 on four seven
segment display LEDs? How many counters?

....................... Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

??? sequence:..........

??? decoder:..........


Decimal displayed:..... 7 9 5 3
(on four 7 segment LEDs)

Are we saying for 10 bit counter when the count reaches 7953 we have:

....................... Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

1 in 10 sequence:...... X X X X

X = HIGH

1 in 10 decoder: (To drive LED driver)


Decimal displayed:..... 7 9 5 3
(on four 7 segment LEDs)

---
Here: (View in Courier)

. DIGIT 4
. COUNT DECODE DISPLAY
. +-----+ +------+ +-----+
. | Q9|---|IN9 g|---|g |
. . . . . . .
. . . . . . .
. . . . . . .
. | Q0|---|IN0 a|---|a |
. +-----+ +------+ +-----+
.
. DIGIT 3
. COUNT DECODE DISPLAY
. +-----+ +------+ +-----+
. | Q9|---|IN9 g|---|g |
. . . . . . .
. . . . . . .
. . . . . . .
. | Q0|---|IN0 a|---|a |
. +-----+ +------+ +-----+
.
. DIGIT 2
. COUNT DECODE DISPLAY
. +-----+ +------+ +-----+
. | Q9|---|IN9 g|---|g |
. . . . . . .
. . . . . . .
. . . . . . .
. | Q0|---|IN0 a|---|a |
. +-----+ +------+ +-----+
.
. DIGIT 1
. COUNT DECODE DISPLAY
. +-----+ +------+ +-----+
. | Q9|---|IN9 g|---|g |
. . . . . . .
. . . . . . .
. . . . . . .
. | Q0|---|IN0 a|---|a |
. +-----+ +------+ +-----+

The clocks into and the carries into/out of the counters aren't shown,
but what happens is that as the count sequence progresses, the outputs
which are hot get decoded so that the LED segments corresponding to
the numerical values of those hot outputs are illuminated.

Okay this is what I understand.


* Each display is a 7 segment LED, which, if you ignore DP has
connections a-g. You obtain all the numerals from powering the seven LED
segments in differing combinations.

* The above shows four 10 bit counters with outputs Q0-Q9. So, we are
still using four ICs to show a count of 7953.

* In a 4 bit decade counter situation, each digit display is proceeded
by a BCD decoder that takes a 4 bit input (Q1-Q4). If you look at the
overall sitiation with the 4 bit situation, we have 16 bits lines that
are decoded, (4 bits or wires for each display decoder, for each digit
display).

* In the above situation each display decoder has 10 lines, taking input
from Q0 to Q9. That requires 40 lines fed to the decoders in total.

* I thought that one, 10 bit counter might have been superior to a 4 bit
counter, in terms of ICs required, but it is not. In fact, is the
MC14017B really a 4 bit decade counter, but having 10 outputs (Q0-Q9)?
That is what it looks like, but it's puzzling.

* I cannot understand why, when you can drive a digit display with 4
bits (only 4 bits required to get up to a count of 10), we have a decade
counter with 10 bits.

* I'm obviously missing something.