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Up counter

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shokka

New Member
in my grade 10 computer engineering class we just covered how to create an 'up counter' which is an astable, with 4 d-latch flipflops attached to it..
We covered how to hook it up to a 7 segment led as well.

I was wondering what exactly is the electronic device that is the counter? like Im sure it must be a chip with 8 outputs.. a, not a, b, not b etc..

I only know what ive learned for the past few months so any help I get would be greatly apreciated :)

Thanks guys
 

ljcox

Well-Known Member
There is a wide variety of IC counters available. Some only count up some only count down and some can be set to count up or down.

Some have binary outputs, some are decade counters (ie. modulo 10) that have binary outputs and count 0 to 9 then back to 0.

Examples of CMOS counters are:-

4020 which is a 14 stage binary ripple counter
40160 which is a presettable decade counter
4516 which is a binary up/down counter
4518 which is a dual synchronous up counter
etc

There are also counters eg. the 4022 and 4017 that have decoded outputs.

Also, shift registers can be configured as either as ring counter or a twisted ring counter.

Len
 

Dean Huster

Well-Known Member
Actually, "astable" describes a free-running "oscillator", such as the astable mode of a 555 timer that outputs a constant rectangular wave of specified frequency. Most counters, such as the TTL 7490 or 74LS192 use a series of four "bistable" flip flops to do the counting, each bistable flip flop representing one bit, four required for a 4-bit binary or one-digit decade counter.

Your final choice of flip flop modes is the monostable mode that outputs a single pulse upon receiving a trigger input. Otherwise known as a "one-shot", the TTL versions are represented by the 74121 and 74123. One-shots come in retriggerable and non-retriggerable versions and like counters, may be either positive- or negative-edge triggered. In the TTL world ALL ripple counters are negative-edge triggered and ALL synchronous counters are positive-edge triggered. The 74123 one-shot can be configured for either positive- or negative-edge triggering.

Dean
 
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