Re: Explanition of a circuits section

[Maurizio Ferraris <ferring-at-inrete.it>]

At 17.07 13/04/01 -0400, you wrote:
>http://www.geocities.com/crankorgan/pikerPG2.jpg
>has a circuit example I think should work for emc.  I have all of the
>parts now, but Im not sure i understand the connection points on  the
>7474 where pins 1 and 4 appear to be tied to +5v, the -o by the four is
>odd to me.
As you may see on the description of the 7474 on the same jgp, also the CLR 
pin should have a dot. In the circuit this means that either SET or CLR are 
ininfluencial, and the output of the flip-flops is only determined by the 
previous state and the DIR input upon each CLK rising edge.
This may open a question during power up, where the output may be set at a 
random value. In any case this circuit cannot output illegal values, just 
it starts at a random point in the sequence. This may not be a problem 
since you usually have to home the motor before using it (I mean you cannot 
just count the pulses, because you never know where you started).
Additionally when you power the circuit, the motor may take a small (max 
one step) random move.
Hope this helps.
Mau.

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Maurizio Ferraris                ferring-at-inrete.it
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