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Re: How can i put the pins of LPC2000-family into high-z?

Started by "sub...@aeolusdevelopment.com" February 27, 2007
Bertrik Sikken Wrote
>On di, 2007-02-27 at 15:39 +0000, tobi_tobias69 wrote:
>> How can i put the ports of the LPC2000-family (LPC2294, LPC2292,
>> LPC2194, LPC2129) into high-z to isolate them from the rest of
>> electronic parts to make ict ? Which pins of the prozessor change the
>> state into high-z ? I didn't found any informations in the datasheets.
>> Thank you.
>
>AFAIK there are no pins that change the state into high-z.

Input is a pretty good approximation to high-z :)

The obvious pin to place most (but not all) pins into high-z is reset :)
As Bertrik said, check the manual.

The lpc2000s do not have any way to hook up an ICE so there is no real need
for them to isolate clock pins etc..

Robert
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An Engineer's Guide to the LPC2100 Series

Using RESET to make all Pins as inputs is mostly correct, but there is a
trap (isn't there always ?).

It is true for Port 0 on all variants as far as I know.
For Port 1, Philips for some reason (??) decided to put weak pull-ups on
all the port pins. Therefore, even programmed as inputs, they will have
an impedance between 60k and 200k Ohms. For your test purposes this is
probably fine, but is a *right* PITA when you are trying to get sleep
current down to a minimum for a typical real application.

Maybe they did this to make Intel 8051 people feel more at home or
something, but I really wish they had been consistent with Port 0. Yes
it is possible to attain the quoted sleep current, but not in a real
application with high port usage (it is nearly impossible to ensure
*all* port 1,2.. inputs are naturally high when in sleep mode, and *all*
outputs happen to want to be high for sleep state). When you are asleep
it is likely other supply rails are off, making the natural state of I/O
in sleep state most probably low !

So, to be accurate; it is impossible to put Port 1 (or >1) into true
Hi-Z mode.

________________________________

From: l... [mailto:l...]
On Behalf Of s...@aeolusdevelopment.com
Sent: Wednesday, 28 February 2007 5:31 AM
To: l...; l...
Subject: Re: [lpc2000] How can i put the pins of LPC2000-family
into high-z?

Bertrik Sikken Wrote
>On di, 2007-02-27 at 15:39 +0000, tobi_tobias69 wrote:
>> How can i put the ports of the LPC2000-family (LPC2294,
LPC2292,
>> LPC2194, LPC2129) into high-z to isolate them from the rest
of
>> electronic parts to make ict ? Which pins of the prozessor
change the
>> state into high-z ? I didn't found any informations in the
datasheets.
>> Thank you.
>
>AFAIK there are no pins that change the state into high-z.

Input is a pretty good approximation to high-z :)

The obvious pin to place most (but not all) pins into high-z is
reset :)
As Bertrik said, check the manual.

The lpc2000s do not have any way to hook up an ICE so there is
no real need
for them to isolate clock pins etc..

Robert

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