Re: Tri State Devices

On Mon, 27 Feb 2006 15:44:10 -0600, "Abstract Dissonance"
<Abstract.Dissonance.hotmail.com> wrote:

Is a Tri State "driver"(I think thats what its called) basicaly a device
which lets you set either Low Z or High Z?

something like

C
|
|------|
A ---| |--- B
|------|


Where, say, if C is high then A and B see a high Z(open circuit) and if C is
low then it acts like a low Z? (a short)


or maybe they are only unidirectional?

But basicaly it is like a controled switch?


The reason I ask cause in a circuit they have something like



D2 >------------+
|
|
|------|
D0 >---------| |---+----- Data
|------| |
|
ACK >-------------------+

Where the device is 74LS244.


Only thing I can figure out is that D2 acts like a control that lets D0 pass
through or not. If its off then ACK "senses" the Data...

i.e.,

So D2 off(or on if inverted) would allow D0 to send data through to Data...
and ACK could "sense" this if it wanted... if D2 was on then D0 couldn't
send anything and ACK could then be used "sense" output comming from Data.

So, in a sense it lets Data be used as an input and output port... but
without the device then data could go to D0 and if D0 is only an output it
will be recieving input which might screw it up?



Is that the basic idea?


---
If it were to be done with relays, here's how it would work:


+V GND
DATA>------+ | |
| O--> |<--O
[COIL]- - -|
| O
GND |
|
OE>--------+ |
| O
[COIL]- - -|
| O--> |
GND |
+------->OUT



DATA | OE | OUT
-------+----+-----
GND GND HI-Z

+V GND HI-Z

GND +V GND

+V +V +V

HI-Z meaning that OUT is floating.





--
John Fields
Professional Circuit Designer
.

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