Need help in understand the "Markers" on electronic chips


by null void
Tags: chips, electronic, markers
null void
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#1
Jan9-14, 11:49 PM
P: 79


I am just wondering what is the markers telling us, like what has shown in the diagram, the CLR is telling us if we apply active-high state input to that port, the flip flop will be reset right? But there is some case where the Markers is labeled as CLR' (bar-CLR) and there is a bubble attached at the port it should be something like "NOT gate". So in this case how do i determine whether should i apply high or low state to reset my flip flop?

If CLR is labeled without bar, does it mean when the port receive high state, ff is reset;
and if CLR is labeled with bar, does it mean when the port receive low state, ff is reset?

Do the bubble determine anything?
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null void
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#2
Jan10-14, 01:13 AM
P: 79


This is the type of flip flop i see in my note, if the CLR port is active-Low, so supplying high state into the port will get inverted by the bubble b4 the port then become low, so can i say the flip flop is reset in this configuration?


But my note keep using this kind of configuration to avoid the flip flop from getting reset...
berkeman
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#3
Jan10-14, 11:16 AM
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No, the bubble is a marker, not an active thing. The bubble indicates active low for inputs, so the CLR~ input clears the FF when it is driven low. And the bubble and > markings on the clock input indicate that the clock causes the data to propagate on the negative-going edge of the clock input.

null void
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#4
Jan10-14, 04:38 PM
P: 79

Need help in understand the "Markers" on electronic chips


oh, is that mean there is no such things like a CLR~ without bubble marker?
berkeman
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#5
Jan10-14, 04:44 PM
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Quote Quote by null void View Post
oh, is that mean there is no such things like a CLR~ without bubble marker?
Correct. No bubble means you use the active high signal CLR. A bubble means that the active low signal CLR~ is used to clear the FF.
null void
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#6
Jan10-14, 04:50 PM
P: 79
Ah I see, thank you very much :)
tfr000
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#7
Jan10-14, 04:51 PM
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Take a look at this, which explains a little about why designers use certain symbols:
http://www.eetimes.com/document.asp?doc_id=1274541

This page also explains some of it about halfway down, under "DeMorgan's Theorem":
http://www.physics.mcmaster.ca/phys4...b/chapter5.htm

Also
http://hyperphysics.phy-astr.gsu.edu...c/gate.html#c2

and this slide show isn't bad
http://webdocs.cs.ualberta.ca/~amara...ams/sld011.htm

I couldn't find any pages that do a fantastic job of explaining this...


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