Mod-5 counter

[digital_geek]

I am trying to build a mod-5 counter and need a schematic for it. Any help it would be appreciated. If possible a schematic using all gates not IC's.

[philba]

It isn't clear what you mean by gates and not ICs. I would guess you are asking for a logic representation of a mod 5 counter. Is this a school assignment? <p>Design a 3 bit counter and take the output that represents 5 as input to reset the counter. pretty simple. Or cascade 5 FFs and pass a "1" in a circle.<p>There are lots of simple IC based solutions but you didn't ask for that...<p>Phil<p>Phil

[Gorgon]

Since you don't want to use ICs, it's complicated to help you. Most gates comes in ICs, and if you don't want to use them, we need to revert to transistors. Using a transistor-only construction is a heavy task, not impossible, but unecessary. But if you want to go this road we'll be almost happy to help you. <p>TOK

[digital_geek]

I am looking for a logic representation!

[rstofer]

The only reason I do homework problems is nostalgia. Given that:<p>Present State..| Next State
===========================
State..D..C..B....D..C..B
---------------------------
0........0..0..0....0..0..1
1........0..0..1....0..1..0
2........0..1..0....0..1..1
3........0..1..1....1..0..0
4........1..0..0....0..0..0<p>From that and a little manipulation we can get the equations for J-K flops as:<p>JB = KB = D' - flop B toggles while D=0
JC = KC = B - flop C toggles when flop B=1
JD = B and C - flop D sets when B=C=1
KD = D - flop D resets when set<p>So, you need 3 J-K flops and an AND gate. This circuit implements the divide by 5 portion of a decade counter. Flop A just divides by 2 and is not included here.<p>Results from Logic Design with Integrated Circuits by Wickes - John Wiley & Sons, Inc 1968 Pages 205-206<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">code:</font><hr><pre> </pre><hr></blockquote><p>[ July 08, 2005: Message edited by: rstofer ]<p>[ July 08, 2005: Message edited by: rstofer ]<p>[ July 08, 2005: Message edited by: rstofer ]<p>[ July 08, 2005: Message edited by: rstofer ]</p>

[rstofer]

Well, you will have to provide your own spacing for the table.

[Chris Smith]

TTL is the basics of all the chips any way. <p>I used to build my own from SCRs and Triacs just for the educational value and Robust ways. <p>Fets make it even easier these days. <p>Its not that hard, and it is a much better visual tool to learn from the old ways than from chips.<p> Soon the young ones will be saying “TTL, what’s that”?

[Newz2000]

"Time to live," right? But what does that have to do with circuits? <p>(jk, I know it's transistor-transistor logic)<p>[ July 08, 2005: Message edited by: Matt Nuzum ]</p>

[philba]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Chris Smith:
TTL is the basics of all the chips any way.
...
<hr></blockquote><p>most chips don't use TTL - they use CMOS. That's the only way to get decent power consumption. I think you confused the logic family with the logic building blocks.

[philba]

duplicate posting. couldn't delete<p>[ July 08, 2005: Message edited by: philba ]</p>

[philba]

does code option not work for tables? I couldn't get it to work correctly If you could use a fixed pitch font, that might work.<p>[ July 08, 2005: Message edited by: philba ]</p>

[L. Daniel Rosa]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr> Soon the young ones will be saying “TTL, what’s that”? <hr></blockquote><p>That's "through the lens", for SLR cameras. "SLR, what's that?"<p>Not even young ones. Not long after I got my driver's license, a few schoolmates took me out to drive in one's father's UAV (urban assault vehicle, a monstrosity of hideous design). When asked if I wanted to drive for a while, I got behind the wheel then asked, "Where's the clutch?" To which the reply came, "What's a clutch?"

[Chris Smith]

Transistors come in all shapes and forms. <p>CMOS, mos, Scr, and the like. <p>TTL merely mentions the use of multiple transistors, or any transistor combination for the logic building block, not which type of transistor will be used. Trans/Trans/Logic<p>TTL used Bipolar, MOS, CMOS, and even gates like SCRS when power was needed. TTL was not a "Family" at First, it was a process for logic. <p>I was not referring to a “Family” of production chips, but rather the building blocks from scratch, like it was done before mass production and Standardization of these chips took over. <p>Many individual circuits were formed, Patented, or invented from this method.

[philba]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Chris Smith:
Transistors come in all shapes and forms. <p>CMOS, mos, Scr, and the like. <p>TTL merely mentions the use of multiple transistors, or any transistor combination for the logic building block, not which type of transistor will be used. Trans/Trans/Logic<p>TTL used Bipolar, MOS, CMOS, and even gates like SCRS when power was needed. TTL was not a "Family" at First, it was a process for logic. <p>I was not referring to a “Family” of production chips, but rather the building blocks from scratch, like it was done before mass production and Standardization of these chips took over. <p>Many individual circuits were formed, Patented, or invented from this method.<hr></blockquote><p>
I was tempted to let this pass but in the event that some one might actually believe that -<p>TTL, in this context, means a specific configuration of bipolar transistors and resistors as well as specific voltage levels for high vs low. No one in the industry would refer to the building blocks of CMOS ICs as TTL. I'd like you to show me a reference that says that TTL was implemented with CMOS (or SCRs for that matter). If you meant "transistors" or gates, then you should have said so. <p>I sure do get tired of people tossing around industry terms trying act like they actually know what they are talking about.<p>I have a little exposure to semiconductor design, having worked at intel for 7 years...<p>Phil

[rshayes]

Phil is correct.<p>The immediate ancestor to TTL (Transistor-Transistor Logic) was DTL (Diode-Transistor Logic). DTL was originally built with discrete components, with diodes as the logic elements and transistors, usually one per gate, providing voltage and power gain. Some of the early integrated logic series implemented these circuits in integrated circuit form.<p>TTL replaced the diodes with multiple emitter transistors. This had advantages when implemented as an integrated circuit, since it avoided the necessity for separate isolation wells for the diodes. This made the integrated circuit smaller and easier to lay out.<p>TTL was never built with discrete parts. The multiple emitter transistors needed were simply not available, and DTL worked just as well. (To be strictly accurate, a few double emitter transistors were marketed for use as choppers. In theory, you could make a two input TTL gate with one of these.)<p>In theory, you could build CMOS gates out of discrete parts. In practice, there are very few p-channel MOS transistors available, and these do not have thae tightly controlled threshold characteristics that you would need for logic circuits.