LXT971A problem

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Hi,

I'm using LXT971A with a Powerpc ppc405EP. The Hotplug function of
device doesn't work.
When I switch on the board with the ethernet cable plugged, the
ethernet link works and I can unplug and replug and it's OK.
But, when I switch on the board with the ethernet cable unplugged, when
I plug it, the autonegotiation doesn't work. I must reset device by
modifiing reset control register.

Have you got an idea about this problem ???
I think it's an hardware configuration problem but Which one ???

thanks in advance for your help


Re: LXT971A problem

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We use the LXT971A on an MPC8250, and it works well.  Did you remember
to put pullup resistors on the LED/CFGn pins (see tables 7 and 9 in
the data sheet)?


================================

Greg Neff
VP Engineering
*Microsym* Computers Inc.
snipped-for-privacy@guesswhichwordgoeshere.com

Re: LXT971A problem
we use 2 leds to display network trafic.
these 2 LED/CFG are pull up to 2,2V
and the last one is pull up to 3,3V
I don't know if this voltage is enough to put input to high position.
You know, don't you ???
Thanks for your help.


Re: LXT971A problem

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2.2V sounds OK, but if the 3.3V supply comes up before the 2.2V supply
then the LXT971A may interpret these two pins as being low at that
time.  You should use pullups to 3.3V.


================================

Greg Neff
VP Engineering
*Microsym* Computers Inc.
snipped-for-privacy@guesswhichwordgoeshere.com

Re: LXT971A problem
I don't know what you mean.
I can't pullup the 2 pins to 3,3V because I use it to display the
network trafic : it is plugged to a led.
Tomorrow, at office, I will see all that and I let you know about that.
Thanks.
See you


Re: LXT971A problem

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When you said 'pulled up to 2.2V' I assumed that you meant to a 2.2V
supply.


================================

Greg Neff
VP Engineering
*Microsym* Computers Inc.
snipped-for-privacy@guesswhichwordgoeshere.com

Re: LXT971A problem
no, there is a LED and a resistor betweeen pin and 3,3V


Re: LXT971A problem
Hi,

I'm at office, and I'm seeing in configuration register (adress 0) that
the 3 LED/CFGn pins are in high state: Speed select, A/N enable and
Duplex mode are at 1.
So it's ok for this point.


Re: LXT971A problem
I've found the problem.
The sleep mode is enable by hardware pin (which is pullup).
If I disable this mode by soft, the hotplug feature is working.
But it's not the solution because in datasheet, I see that the device
can be waked up from sleep mode if there is activity on the connetor
(so by plugging an ethernet cable).
In my case, the device is not waked up.
Why ??? I don't know

Any ideas ???


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