Synchronous and asynchronous confusion.

Thread Starter

hp1729

Joined Nov 23, 2015
2,304
We just don’t have enough words to go around. Latches have synchronous and asynchronous inputs. Inputs that work in relation to a clock pulse are synchronous. “J”, “K” and “D” inputs, for example, cause nothing to happen themselves. They require a clock pulse. Inputs that cause an immediate result are asynchronous. “Set”, “Reset”, “Clear” and such are typical asynchronous inputs. In general asynchronous inputs override synchronous inputs. Simple enough.


Then there are synchronous and asynchronous counters that both require a clock pulse. Synchronous counters implies that all the counter outputs change state at the same time, triggered by a single clock pulse. Asynchronous counters, ripple counters, change state in sequence. Lower stages changing state cause upper stages to change state. The count ripples up through the stages. In ripple counters there may be a period of some 50 ns where the outputs are not a valid count and can cause glitches in operation.


All that being said a synchronous or asynchronous counter can have a certain function be synchronous or asynchronous. A common clear input or presettable inputs may be synchronized to the counting clock pulse or be asynchronous.


Synchronous serial communication implies that a separate clock pulse is used to control the timing of the data bits. Absolute speed is not so much a concern. Asynchronous serial communication implies that data bits are sent at a specified time frame. Speed is very important.

In synchronous communications data speeds can be slowed down to the speed of manual switch operations. In asynchronous communication systems the speed at which data is sent must be organized so it is received at the same speed.
 

Papabravo

Joined Feb 24, 2006
13,963
It is hard to square the use of the word confusing with such a thorough exposition of the situation. I followed it all without difficulty and most of it seemed self-evident.
 

crutschow

Joined Mar 14, 2008
25,131
The confusion is the title of your post. ;)

By convention, this forum is generally for questions about electrical or electronic matters and I would prefer to keep it that way.
That way I won't have to waste my time reading through somebody's long winded rant about something I already know to find out he/she didn't have a question. :rolleyes:
Such rants belong elsewhere, such as the Blog section.
 
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Thread Starter

hp1729

Joined Nov 23, 2015
2,304
Is there a question or was that just a rant?
Not a question. Not a rant. Just information I see referred to incorrectly on different threads. Info for the noobs. Something to find on a search of the topics.
The confusion is the title of your post. ;)

By convention, this forum is generally for questions about electrical or electronic matters and I would prefer to keep it that way.
That way I won't have to waste my time reading through somebody's long winded rant about something I already know to find out he/she didn't have a question. :rolleyes:
Such rants belong elsewhere, such as the Blog section.
Sorry. In the future I will put such things in the blog, if I post them at all.
 
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