In article <v6ajh2dooso3ainioosi3a2d8nvg8ulo2e@4ax.com>,
 Jack Klein <jackklein@spamcop.net> wrote:

> On Tue, 26 Sep 2006 12:54:43 GMT, Al <no.spam@wanted.com> wrote in
> comp.arch.embedded:
> 
> > In article <1159253045.224484.153890@i3g2000cwc.googlegroups.com>,
> >  "uzinei" <uzinei@gmail.com> wrote:
> > 
> > > Hi, I am developing a data transmission circuit using the Cypress
> > > EZ-USB development kit.
> > > I have a question about setting register. When I unenable a certain
> > > pin, for example, CLKOUT pin, it have to be 0 Voltage, I think.
> > > But although the CLKOUT pin become to be float, it still outputs 2.5
> > > Volt. Is it correct? Or, because of wrong firmware I made, it become to
> > > 2.5 Volt, not to 0 Volt?
> > > I am a beginner, so I have to study hard about USB.
> > > But if you help me, it is very helpful for me. Please teach me.
> > > Thank you for any help. Bye!!
> > > 
> > 
> > An output that is disabled will float to the voltage present at whatever 
> > it is connected to.
> > 
> > Also, since ones and zeros in TTL are defined as being > 2.7V or < 0.7V, 
> 
> No, the logic levels in real TTL are <= 0.7V for low and >= 2.0V for
> high.
> 
> > it is neither a one nor a zero. It is "floating."

No, check your data sheet. You're talking about "Recommended Operating 
Conditions." I'm talking about "DC Electrical Characteristics."

The actual levels depend upon your definition; is it Vih or Voh that 
you're talking about. He is asking about Voh and in the refernence, Voh 
is 2.4V .

http://www.mines.edu/Academic/courses/physics/phgn317/lect03/sld005.htm

The actual value depends upon the testing conditions. On the data sheet 
I'm looking at, Voh for a commercial product is 2.7V .

Al

On Tue, 26 Sep 2006 12:54:43 GMT, Al <no.spam@wanted.com> wrote in
comp.arch.embedded:

> In article <1159253045.224484.153890@i3g2000cwc.googlegroups.com>,
>  "uzinei" <uzinei@gmail.com> wrote:
> 
> > Hi, I am developing a data transmission circuit using the Cypress
> > EZ-USB development kit.
> > I have a question about setting register. When I unenable a certain
> > pin, for example, CLKOUT pin, it have to be 0 Voltage, I think.
> > But although the CLKOUT pin become to be float, it still outputs 2.5
> > Volt. Is it correct? Or, because of wrong firmware I made, it become to
> > 2.5 Volt, not to 0 Volt?
> > I am a beginner, so I have to study hard about USB.
> > But if you help me, it is very helpful for me. Please teach me.
> > Thank you for any help. Bye!!
> > 
> 
> An output that is disabled will float to the voltage present at whatever 
> it is connected to.
> 
> Also, since ones and zeros in TTL are defined as being > 2.7V or < 0.7V, 

No, the logic levels in real TTL are <= 0.7V for low and >= 2.0V for
high.

> it is neither a one nor a zero. It is "floating."

-- 
Jack Klein
Home: http://JK-Technology.Com
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In article <1159253045.224484.153890@i3g2000cwc.googlegroups.com>,
 "uzinei" <uzinei@gmail.com> wrote:

> Hi, I am developing a data transmission circuit using the Cypress
> EZ-USB development kit.
> I have a question about setting register. When I unenable a certain
> pin, for example, CLKOUT pin, it have to be 0 Voltage, I think.
> But although the CLKOUT pin become to be float, it still outputs 2.5
> Volt. Is it correct? Or, because of wrong firmware I made, it become to
> 2.5 Volt, not to 0 Volt?
> I am a beginner, so I have to study hard about USB.
> But if you help me, it is very helpful for me. Please teach me.
> Thank you for any help. Bye!!
> 

An output that is disabled will float to the voltage present at whatever 
it is connected to.

Also, since ones and zeros in TTL are defined as being > 2.7V or < 0.7V, 
it is neither a one nor a zero. It is "floating."

Al

Hi, I am developing a data transmission circuit using the Cypress
EZ-USB development kit.
I have a question about setting register. When I unenable a certain
pin, for example, CLKOUT pin, it have to be 0 Voltage, I think.
But although the CLKOUT pin become to be float, it still outputs 2.5
Volt. Is it correct? Or, because of wrong firmware I made, it become to
2.5 Volt, not to 0 Volt?
I am a beginner, so I have to study hard about USB.
But if you help me, it is very helpful for me. Please teach me.
Thank you for any help. Bye!!