How to implement a special count secuence using a common TTL

[Lathe_Biosas]

Hi

I would like to use a common 12 Bit TTL counter to count from say from
100 to 1000 and start again from 100. As for know the master reset pin
is used to count from 0 to 1024 but I don't have any idea to begin the
count with 100 and finish it at 1000.

Is there an easy way to do these or the only way is to add AND and OR
gates?

Sorry about the ignorance but I don't know how to do it, any ideas
would be kindly appreciated
Best Regards

 

[Mochuelo]

On 19 Jul 2005 04:44:39 -0700, "Lathe_Biosas"
<lathe_biosas@hotmail.com> wrote:

Hi

I would like to use a common 12 Bit TTL counter to count from say from
100 to 1000 and start again from 100. As for know the master reset pin
is used to count from 0 to 1024 but I don't have any idea to begin the
count with 100 and finish it at 1000.

Is there an easy way to do these or the only way is to add AND and OR
gates?

Sorry about the ignorance but I don't know how to do it, any ideas
would be kindly appreciated
Best Regards

If the counter does not have parallel load, it will always count from
zero (when you reset it).

To make it wrap after a count value other than 4095, yes, you need
additional logic.

I would use a CPLD for that (or a microcontroller, if you don't need
extremely short delay times).

 

[martin griffith]

On 19 Jul 2005 04:44:39 -0700, in sci.electronics.design
"Lathe_Biosas" <lathe_biosas@hotmail.com> wrote:

Hi

I would like to use a common 12 Bit TTL counter to count from say from
100 to 1000 and start again from 100. As for know the master reset pin
is used to count from 0 to 1024 but I don't have any idea to begin the
count with 100 and finish it at 1000.

Is there an easy way to do these or the only way is to add AND and OR
gates?

Sorry about the ignorance but I don't know how to do it, any ideas
would be kindly appreciated
Best Regards
Its a long time since I've done TTL, butI think you need a down

counter, not an up counter.
IIRC many downcounters will preload a new count when it hits zero.

Just think backwards




martin

 

[Mochuelo]

On Tue, 19 Jul 2005 15:06:07 +0200, Mochuelo <b@b.b> wrote:

If the counter does not have parallel load, it will always count from
zero (when you reset it).

I should have said "If the counter does not have neither parallel nor
serial load, it will always [...]", but I directly discarded the
cumbersome serial option.

 

[John Fields]

On 19 Jul 2005 04:44:39 -0700, "Lathe_Biosas"
<lathe_biosas@hotmail.com> wrote:

Hi

I would like to use a common 12 Bit TTL counter to count from say from
100 to 1000 and start again from 100. As for know the master reset pin
is used to count from 0 to 1024 but I don't have any idea to begin the
count with 100 and finish it at 1000.

Is there an easy way to do these or the only way is to add AND and OR
gates?

Sorry about the ignorance but I don't know how to do it, any ideas
would be kindly appreciated

---
If you want to count in binary you will need three presettable 4 bit
counters, like 74HC160's or 162's, but if you want to count in BCD you
will need four presettable BCD counters, like 161's or 163's.

In either case you will need to decode the 1000 state with external
logic and use that to load the counter with 100.

What is your application?

--
John Fields
Professional Circuit Designer

 

[Mark Zenier]

In article <925qd1t2ebu02uisq6om97uipf42hcdo76@4ax.com>,
John Fields <jfields@austininstruments.com> wrote:

If you want to count in binary you will need three presettable 4 bit
counters, like 74HC160's or 162's, but if you want to count in BCD you
will need four presettable BCD counters, like 161's or 163's.

74?160 BCD with asynchronous Clear
74?161 4 Bit with asynchronous Clear
74?162 BCD with synchronous Clear
74?163 4 bit with synchronous Clear

(If you need a glitchless power up reset, use the '160 or '161).

In either case you will need to decode the 1000 state with external
logic and use that to load the counter with 100.

What he said. If you want to count from 100 (or any arbitrary number)
to 999, you can simplify the decoder by using the "Ripple Carry" Outputs
of three '160s (or '162s) by combinding these with a Nand gate and
connecting that to the "Load" control input of the three chips, with
the preset "data" inputs of the three counters set to the selected value.

Mark Zenier mzenier@eskimo.com Washington State resident

 

[keith]

On Tue, 19 Jul 2005 04:44:39 -0700, Lathe_Biosas wrote:

Hi

I would like to use a common 12 Bit TTL counter to count from say from
100 to 1000 and start again from 100. As for know the master reset pin
is used to count from 0 to 1024 but I don't have any idea to begin the
count with 100 and finish it at 1000.

Is there an easy way to do these or the only way is to add AND and OR
gates?

Make you counter count up (or down) and feed it into a ROM. The address
of the ROM is the acounter values, and the data in the appropriate
locations anything you wish. Reserve an output for a reset/preload.
Optimise as necessarty to fit. ;-)

Sorry about the ignorance but I don't know how to do it, any ideas would
be kindly appreciated
Best Regards

--
Keith

 

[Glenn Gundlach]

John Fields wrote:

On 19 Jul 2005 04:44:39 -0700, "Lathe_Biosas"
lathe_biosas@hotmail.com> wrote:

Hi

I would like to use a common 12 Bit TTL counter to count from say from
100 to 1000 and start again from 100. As for know the master reset pin
is used to count from 0 to 1024 but I don't have any idea to begin the
count with 100 and finish it at 1000.

Is there an easy way to do these or the only way is to add AND and OR
gates?

Sorry about the ignorance but I don't know how to do it, any ideas
would be kindly appreciated

---
If you want to count in binary you will need three presettable 4 bit
counters, like 74HC160's or 162's, but if you want to count in BCD you
will need four presettable BCD counters, like 161's or 163's.

In either case you will need to decode the 1000 state with external
logic and use that to load the counter with 100.

What is your application?

--
John Fields
Professional Circuit Designer

Tiny boo boo, John. The '161 and '163 are binary. '160 and '162 are the
BCD counters. Check

http://www.onsemi.com/pub/Collateral/MC74HC161A-D.PDF

Of course if speed isn't needed, state machine (EPROM) counters are
very versatile.
GG

 

[Keith Williams]

In article <pan.2005.07.20.02.08.41.981858@att.bizzzz>, krw@att.bizzzz
says...

On Tue, 19 Jul 2005 04:44:39 -0700, Lathe_Biosas wrote:

Hi

I would like to use a common 12 Bit TTL counter to count from say from
100 to 1000 and start again from 100. As for know the master reset pin
is used to count from 0 to 1024 but I don't have any idea to begin the
count with 100 and finish it at 1000.

Is there an easy way to do these or the only way is to add AND and OR
gates?

Make you counter count up (or down) and feed it into a ROM. The address
of the ROM is the acounter values, and the data in the appropriate
locations anything you wish. Reserve an output for a reset/preload.
Optimise as necessarty to fit. ;-)

Now that I have my engineering hat back on...

Just take an appropriately sized ROM (1Kx10 bits for binary values) and
register with the ROM in the feedback loop to the register. Each ROM
location points to the next "state" with the final state pointing back
to the first. The encoding in the ROM (count sequence) can be anything
you want.

Sorry about the ignorance but I don't know how to do it, any ideas would
be kindly appreciated
Best Regards

--

Keith

 

[Lathe_Biosas]

Hi

Thank you very much for all the great ideas. I thought it was more
trivial.

The bus will be parallel loaded via a PCI interface, I was trying to
check my circuit with a counter sending diferent values at some
frecuency and avoid for the moment programming a PCI card but it will
be better to go ahead with the PCI card

Best Regards