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Simple question

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Circuit: input - debouncer - 4026 - 7 seg

one could connect in other 4026b chips in order to show multiple digits e.g 2 chips up to 99 3 chips 999 4 chips 9999 Etc.

This could be done by connecting pin 5 of the first IC and to the clock of the next ETC.

So how doe they actually know how to work and in what order ?. is their binary involved? Why is it that they just all increase by one once the input is high, How do the ICs know how to count up in order?
 
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Hy John,

I can tell that you are intrigued by digital electronics and are somewhat mystified by it- as I was when the first digital chips became freely available in the 1960s.

To answer one of you questions- yes, to make a counter, only binary is involved (other digital states, most notably ternary, can be used but are rare).

For the most common binary logic family, the 74 series transistor transistor logic (TTL) family, a logic 1 is 5V and a logic 0 is 0V (this is not exactly true, but just assume so). The other thing to know is that you can make every logic function from a simple counter to a microprocessor to a gigabyte memory with just two fundamental logic functions: NOR (invert) and a two input gate, either AND or OR, assuming an unlimited number of those functions that is.

You ask how does a counter know how to count. The answer is because a fairly large number of the two fundamental binary functions are hard wired to do so using digital, binary design techniques

Once you get the hang of it, making a counter from the two fundamental binary logic functions is quite straight forward.

Incidentally, the first 74 series logic chip was the 7400 which is a QUAD TWO INPUT NOR (correction NAND) GATE. As this chip has both the fundamental functions in one gate, it follows that you can make any binary function with an unlimited number of 7400 chips. In fact, that is pretty much what is inside the counter chips.

spec
 
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Incidentally, the first 74 series logic chip was the 7400 which is a QUAD TWO INPUT NOR GATE. As this chip has both the fundamental functions in one gate, it follows that you can make any binary function with a number of 7400 chips. In fact, that is pretty much what is inside the counter chips.
spec , Big respect but you meant NAND of course :oops:
 
Hy John,

I can tell that you are intrigue by digital electronics and are somewhat mystified by it- as I was when the first digital chips became freely available in the 1960s.

To answer one of you questions- yes, to make a counter, only binary is involved (other digital states, most notably ternary, can be used but are rare).

For the most common binary logic family, the 74 series transistor transistor logic (TTL) family, a logic 1 is 5V and a logic 0 is 0V (this is not exactly true, but just assume so). The other thing to know is that you can make every logic function from a simple counter to a microprocessor to a gigabyte memory with just two fundamental logic functions: NOR (invert) and a two input gate, either AND or OR, assuming an unlimited number of those functions that is.

You ask how does a counter know how to count. The answer is because a fairly large number of the two fundamental binary functions are hard wired to do so using digital, binary design techniques

Once you get the hang of it, making a counter from the two fundamental binary logic functions is quite straight forward.

Incidentally, the first 74 series logic chip was the 7400 which is a QUAD TWO INPUT NOR GATE. As this chip has both the fundamental functions in one gate, it follows that you can make any binary function with a number of 7400 chips. In fact, that is pretty much what is inside the counter chips.

spec

Not really following,:confused: the 4026 is basically a bunch of logic gates?
So the 4026 is made of a number of 7400 chips?
and when a certain voltage is meant it goes high meaning numbers increment by one as each output goes high due to a high voltage?
 
spec , Big respect but you meant NAND of course :oops:
Thanks grand- as I said before, I make mistakes all the time, but I try to keep them big so they are obvious :wideyed:

Post corrected

spec
 
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Not really following,:confused: the 4026 is basically a bunch of logic gates?
So the 4026 is made of a number of 7400 chips?
and when a certain voltage is meant it goes high meaning numbers increment by one as each output goes high due to a high voltage?

Hy John,

Firstly, I made another major mistake and assumed that the CD4026 is part of the 74xxx series family of logic chips, but it's not. It is part of the CD4xxx Complimentary Metal Oxide Silicon [Semiconductor] (CMOS) family. In the CD4xxx family, a hex NOR gate is the, CD4009, a quad TWO INPUT AND gate, CD4011, and a quad TWO INPUT NOR gate, CD4002.

But the mistake makes no difference to the principle of the explanation. The 74xxx and CD4xxx are the two major logic families in electronics, but the former now predominates, so much so, that the original TTL logic functions and pin outs are now made in CMOS too. CMOS is now the most widely deployed technology in digital integrated circuits: memory, microprocessors etc, but that CMOS is fantastically advanced and is based on unbelievably small geometries, resulting in lightning fast speeds and relatively low power consumption.

Basically TTL is fast but consumes a considerable amount of current from the 5V supply rail. On the other hand, CMOS is relatively slow (in electronic terms) and consumes virtually no current from the 5V supply rail. CMOS does consume current though when it is switching and it also consumes any current that it may need to drive loads, like LEDs, on its outputs.

The principal that any logic function, never mind how large or complicated, can be made from an unlimited number of the two fundamental logic functions: NOR and TWO INPUT AND or TWO INPUT OR, holds true for any binary logic family, even rudimentary relay logic.

Because NAND and NOR gates embody both of theses fundamental logic functions in one chip, it is possible (but not necessarily practical) to make any logical binary function from an unlimited number of TWO INPUT NAND gates or TWO INPUT NOR gates.

Yes, the CD4026 is essentially made from the two fundamental logic functions, and it would be a simple but laborious task for a logic designer, like many on ETO, to make a CD4026 from a bunch of TWO INPUT NAND GATES: CD4011.

But a digital IC designer would not literally use the circuit of the individual chips that you see. Instead, he would have libraries of functions that he would copy and paste to generate a mask to fabricate the chip required in silicon. The reason why he would not necessarily use the circuit of individual chips is that his requirements are different to the requirements for general use. One of the main characteristics being output current drive capability.

To illustrate that more complex logic functions are made up of combinations of the fundamental logic functions have a look at the schematics for the actual CD4026: https://www.ti.com/lit/ds/symlink/cd4026b.pdf

In general you can stimulate a logic system by:
(1) a DC logic level, either 0 or 1
(2) a momentary pulse, either 0 or 1
(3) an edge, either rising or falling.

Most flip flops, counters, and shift registers are stimulated by an edge of the clock input, invariably the positive edge.

If you are keen to get a feel for digital electronics you best move would be to familiarize yourself with the following chips in order:
(1) Quad TWO INPUT NAND GATE: 74xxx00
(2) Dual D TYPE FLIPFLOP (positive edge clock, asychronous preset and clear. Q and /Q outputs): 74xxx74
(3) FOUR BIT BINARY COUNTER: 74xxx93
(4) EIGHT BIT SHIFT REGISTER (serial in, parallel in, serial out, parallel out): 74xxx299 (the 4 bit 7495 and 74LS395 are simpler to understand but both of theses chips are now obsolete)
(5) Quad TWO INPUT EXCLUSIVE OR GATE: 74xxx86

A flipflop, or bistable (two stable states, either 0 or 1), can be configured as a one bit counter. Counters and shift registers are nothing more than flip flops connected in series with some gating, each flipflop representing one bit. Once you have mastered the 74xxx74 D type flipflop, you will have made a major leap into the field of digital electronics. :cool:

You may wonder why the simple 74xxx86 gate is at the end of the list- you will find out. :D It is one one the simplest logic chips, but it is capable of some very sophisticated functions, cryptography for example.

Compared to your present academic studies, understanding/designing logic functions should be like falling off a log. A day with a logic designer would do it. There are also a load of excellent books. :)

One last bit of avuncular advise is to familiarize yourself with basic binary arithmetic and ASCI- all dead easy. Once again, there are some excellent books.

In case you think I am oversimplifying logic design, that is true. It is a vast and very complex field, involving advanced maths of all types and special design techniques, especially to execute logic functions fast. But, what I am saying is that the basics are very simple. Also, digital electronics, both practical and theoretical, is absolutely fascinating, at least I think so. :happy:

spec

DATA SHEETS
(1) 74xxx00 NAND gate
**broken link removed**
(2) 74xxx74 D TYPE FLIP FLOP
**broken link removed**
(3) 74xxx93 BINARY COUNTER
**broken link removed**
(4) 74xxx299 SHIFT REGISTER
https://www.ti.com/lit/ds/symlink/cd54hc299.pdf
(5) 74xxx86 EXCLUSIVE OR GATE
**broken link removed**

NOTE: 74HCTxxxx logic chips are high speed CMOS with TTL IO characteristics
 
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I cut my teeth as it were on SN74 TTL , although my projects were a bit of a rats nest , this was my early attempt at a MiDi interface for a 2 manual ELKA organ ,( HC and LS chips) my favourite IC however was the 8255 here it scanned the 132 note keys, in about 5 msec. CDP6402 if I remember is a composite video display driver, the board hung on to a Maplins Z80 development board... as a note I could not have done it without a scope. …. great fun ..
Edit... memory was wrong 6402 is a UART , recall now the empty socket should have a MAX232 and several caps.
midiif.jpg
 
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I cut my teeth as it were on SN74 TTL , although my projects were a bit of a rats nest , this was my early attempt at a MiDi interface for a 2 manual ELKA organ ,( HC and LS chips) my favourite IC however was the 8255 here it scanned the 132 note keys, in about 5 msec. CDP6402 if I remember is a composite video display driver, the board hung on to a Maplins Z80 development board... as a note I could not have done it without a scope. …. great fun ..
View attachment 98969

That made me smile- fond memories of similar boards. The first biggy was a hand-wired rip-off of the PC that preceded the BBC computer, the Acorn Atom. :happy:

6402 CPU and 8255 parallel IO controller- great fun as you say.

spec
 
That made me smile- fond memories of similar boards. The first biggy was a hand-wired rip-off of the PC that preceded the BBC computer, the Acorn Atom. :happy:

6402 CPU and 8255 parallel IO controller- great fun as you say.

spec

I wish I knew what you guys were talking about! :D
 
Maybe I am older than you guys. I learned logic with RTL, then DTL, then TTL, then LS-TTL then I threw away my TTL Cookbook and used Cmos then HC-Cmos for all logic circuits I designed.
 
Maybe I am older than you guys. I learned logic with RTL, then DTL, then TTL, then LS-TTL then I threw away my TTL Cookbook and used Cmos then HC-Cmos for all logic circuits I designed.
I learned logic with:
(1) Discrete: RRL, (relay, relay) then RVL (resistor valve), then RDL, then RTL,
(2) Integrated: TTL and CMOS, then LS-TTL and S-TTL then ECL, them PECL and lots of NMOS, PMOS etc along the way.

Do you remember the days when you would stand on your head just to save a single component. I did a circuit to convert a telephone from dial to push button with RDL: full of very expensive silicon diodes.

The plug in modules on a mobile radar system we made, measured about 18 inches by 12 inches by 1 inch and comprised an aluminum plate. They were hand-wired on miniature PTFE through pins and the TO5 transistors were mounted upside down in rubber grommets- great for heat sinking. One module had nine flip flops that could toggle at 100 KHz too- real state of the art. :D

For home work, in the days when components were expensive/scarce, rather like some of our friends in other parts of the world now, I used to buy old computer boards from the States and strip them for components. Many of the boards were full of IS44, silicon diodes with a few TO5 transistors. I also managed to buy a load of Brit boards: each had four OC28s, which were germanium power transistors that could handle as much as 5A. They came in beautiful chrome plated TO3 copper cases and blew up as soon as you looked at them. I did a bit of modern art and made a picture comprising rows of dead OC28s stuck on with epoxy. Those were the days. :happy:

spec
 
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I updated office computers a long time ago. The operating system was punched cards and the RAM memory was thousands of tiny donuts of ferrite hanging on a maze of wires. No pcb, everything was wire wrapped on millions of square pins. I fixed a problem by piggy-backing a DTL logic IC on top of another DTL IC.
 
I had a computer that was acting up. A DEC technician came in and adjusted the system clock by moving a blob of solder along two very long, spiraling copper traces.
 
I updated office computers a long time ago. The operating system was punched cards and the RAM memory was thousands of tiny donuts of ferrite hanging on a maze of wires. No pcb, everything was wire wrapped on millions of square pins. I fixed a problem by piggy-backing a DTL logic IC on top of another DTL IC.
Do you remember those wire wrap back planes- looked like a rats nest. :arghh: I went to a seminar about the new wire wrap technique. One company even had a computer/robot that would automatically do wire wrap back planes. Long after the wire wrap fashion died, we still used wire wrap wire for hooking up prototype circuits- not the first thicker white stuff but the thin multicolored type.

Those core memory boards were works of art. The high current row and column driver transistors were very useful for home projects- they cost the earth to buy new.

spec
 
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John , you may have noticed your 'simple question' has turned into a trip down memory lane :) For me in the early days engineers had to concentrate hard on logic, and testing etc referring to massive circuit diagram books ( 50 pages of A3 or even A2 was common ) it must have burnt into our brains.
 
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John , you may have noticed your 'simple question' has turned into a trip down memory lane :) For me in the early days engineers had to concentrate hard on logic, and testing etc referring to massive circuit diagram books ( 50 pages of A3 or even A2 was common ) it must have burnt into our brains.
Eh By Gum, these young lads don't know they are born these days. None of this integrated circuit stuff when I were a lad. We had to build gates, flip flops, counters etc, out of resistors, capacitors, diodes, and transistors. Not only that, but we had to mine and smelt the lead and tin for our solder ourselves. I used to get up before going to bed, run twenty miles to work, come rain hail and snow, designing circuits all the way. Then get reported by the guard room for being late for the five am shift. There was tombs of information to wade thru about speeding up transistors, steering diodes and all sorts of stuff like that. To get flip flops to toggle at 1Mhz was a sweat.

As for equipment manuals- eh we were lucky if we had any but, even if we did, they were atrocious: no data flow, riddled with errors and schematics with signals snaking from one sheet to another. No, mostly we had to write our own manuals, with pen an ink too- no fancy word processors for us.

muck & bullets spec :D
 
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