How does a D-FF function?

[azurenel]

Hi,
I'm really dumb when it comes to electronic devices.To make matters worse,I have this project concerning the use of 3 D-FF components.Plus,everything I'm learning is in Japanese(I'm a foreign student in Japan,furthering studies under Electronic Control Engineering).

At the moment,I'm desperately trying my best to understand the Japanese language plus learn new subjects such as Electronic Circuits,Electrical Circuits and so on.So,if there's anyone there who can give me some help understanding,I'd really appreciate it!

 

[WA]

Like any FF, It depends on its' truth table for its' function.

Usually D-FF's are clocked. The main thing is the output usually follows the input after its' clocked.

A standard truth table is...

D__Q__|Q+1 (output)
---------------
0__0____0
0__1____0
1__0____1
1__1____1

As you can see, If D is high Q+1 (the +1 = after clock) is high.

D-FF's are usually used as latches. but they usually used in Johnson and Ring counters.

You should be able to find some books about FF's. They are usually in digital designs or applications type books.

Hope this helps out in getting you started.
wa
P.S. Gambatte Kudasai. Nihon go wa watashi ni totemo muzukashi desu. :wink:

 

[moira]

in cpld/fpga,
u can use dff to implement dividing frequency,
and Jitter-Eliminating circuit

 

[dynoboy]

Hi,
Ok seems like you really dont have much idea about things...so initially I will start it, with the basics..
Alright, you must be knowing the difference between Clocked and Non-Clocked.
The difference is that for Clocked Circuits the output transistion takes place only at some event on the Clock edge, either rising or falling.

For the Non Clocked logic the output if affected always provided the enable (thats what they call it) is High / Low (dependint on the Active State).

Now the devices are differentiated on the basis of this scheme, so always Flip Flops are Clocked and Latches are Non-Clocked.

Thats the start, Ok so even for the D flip flop you are gonna have D-latch and the D Flip Flop.

In the case of the D latch the O/P will tak the value of the input directly provided that the Enable signal is Active.
So there is no delay.
But in case of the D Flip Flop the output is affected by the input anytime there is a transistion on teh clock (posedge -> rising edge, or negedge -> falling edge).
So in the flip flop when ever there is a transistion on the clock teh output will become the input, then after that the input may take any value the output will not change.

Thats all abt the D flip flop.

The Truth Table will be::

For the D flip flop:

I/p O/P Clk Event
1.......1.........Rising Edge (for the rising edge flop),
0.......1.........Stable clock (the flop is set but no transistion of the
..........................................clock so the o/p does not change)

The similar thing will happen for the Faling Edge.

THen there are crtain advanced concepts such as Set Up Time and the Hold Time...for any further info regarding you caould send across a mail to me at: sandeep_a_singh@yahoo.com

Thats all, enjoy the World of electrons

 

[Sergiu_Q]

i upload for you a few "digital circuits" lessons

 

[delay]

The way D flop works it takes (registers) the bit when the clock transits from low to high (or it could be high to low too). That is the D flop is edge triggered. It looks for that rising or falling edge of the clock to move data inside as oppsed to a D latch which inputs data when the clock signal is high or stable , i.e., the D latch is level triggered.

delay (delayed by technology)

 

[maharshi_qis]

DFF means delay FF which produce the same o/p as i/p afetr some delay..

 

[Alkakkali]

Hi..,

Digital systems can be divided into two types :
Combinational
Sequential

The Flip flops is under sequential type and simply it is a memory element to store a bit of data. it can be RS FF or JK FF or D-ff.

D ff has only one input D and a CLOCK signal and at the output Q and Q'

the output Q = D input when the clock is applied, for example if D=0 the Q=0 Q'=1 when clock pulse arrived.


As an Advice i think you need to get more informations by reading a good book in digital electronics.

Regards