Lpc2000

I have read in the LPC214x user manual that some I/O could have 10 ns
slew rate control.
Does it mean that their slew rate can be configured ? because I have
not found any registers that could allow to configure the slew rate of
each I/O functions...

That could be an interesting feature but I'm sure to have correctly
understood

Any helps appreciated!!!

How did you interpret the specs to say that you could have slew rate 
control????

The "data sheet" covers the static and dynamic electrical 
characteristics of the device but like most common digital devices these 
figures are fairly normal. 10ns is given as the typical rise and fall 
time of the outputs "as measured", not guaranteed, and certainly not 
programmable.

------------------ DATA SHEET EXTRACT ---------------------
PORT PINS              min typ max Unit
tr(o) output rise time -   10  -   ns
tf(o) output fall time -   10  -   ns

Typical ratings are not guaranteed.
The values listed are at room temperature (+25 \ufffdC), nominal supply voltages.
--------------------------------------------

Although you are welcome to ask questions it will help you to read and 
compare data sheets for other chips and digital logic in general etc. 
Try thinking about it a little more before being tempted to ask a 
question. The answers you find yourself tend to be far more valuable 
than the ones handed to you. You can be taught a lot of things but you 
only really learn and understand when you "nut it out". It's a bit like 
being a passenger in a car traveling to somewhere where you have never 
been before and then not being able to find the place again by yourself. 
But once you do find it, it's like this clear mental picture that's 
locked in your mind enabling you to vary the route and still get there.

*Peter*

croquettegnu wrote:

> I have read in the LPC214x user manual that some I/O could have 10 ns
> slew rate control.
> Does it mean that their slew rate can be configured ? because I have
> not found any registers that could allow to configure the slew rate of
> each I/O functions...
>
> That could be an interesting feature but I'm sure to have correctly
> understood
>
> Any helps appreciated!!!

Hello Peter,

I know what is a slew rate, do not worry about that and I had found
this figures but I just wanted to know if the term __control__ in slew
rate control extracted from the user manual signified that there is a
way to change it
Because as you probably know, changing this value could be very
interesting regarding CEM...

Regards

--- In lpc2000@yahoogroups.com, Peter Jakacki <peterjak@...> wrote:
>
> How did you interpret the specs to say that you could have slew rate 
> control????
> 
> The "data sheet" covers the static and dynamic electrical 
> characteristics of the device but like most common digital devices
these 
> figures are fairly normal. 10ns is given as the typical rise and fall 
> time of the outputs "as measured", not guaranteed, and certainly not 
> programmable.
> 
> ------------------ DATA SHEET EXTRACT ---------------------
> PORT PINS              min typ max Unit
> tr(o) output rise time -   10  -   ns
> tf(o) output fall time -   10  -   ns
> 
> Typical ratings are not guaranteed.
> The values listed are at room temperature (+25 °C), nominal supply
voltages.
> --------------------------------------------
> 
> Although you are welcome to ask questions it will help you to read and 
> compare data sheets for other chips and digital logic in general etc. 
> Try thinking about it a little more before being tempted to ask a 
> question. The answers you find yourself tend to be far more valuable 
> than the ones handed to you. You can be taught a lot of things but you 
> only really learn and understand when you "nut it out". It's a bit like 
> being a passenger in a car traveling to somewhere where you have never 
> been before and then not being able to find the place again by
yourself. 

> But once you do find it, it's like this clear mental picture that's 
> locked in your mind enabling you to vary the route and still get there.
> 
> *Peter*
> 
> croquettegnu wrote:
> > I have read in the LPC214x user manual that some I/O could have 10 ns
> > slew rate control.
> > Does it mean that their slew rate can be configured ? because I have
> > not found any registers that could allow to configure the slew rate of
> > each I/O functions...
> >
> > That could be an interesting feature but I'm sure to have correctly
> > understood
> >
> > Any helps appreciated!!!
>

Ahh, I see the pin configuration footnotes in the user manual! When the 
chip is being designed at the silicon level, output drivers can be 
specified for various levels of drive and slew rate. This is really very 
similar to fpga chips where you can configure the amount of drive and 
slew rate, but only at the design level.

Although the silicon is capable of driving the lines faster this has 
side-affects such as increased noise in the way of current spikes on the 
chip supply and also increased EMI. In the old days a chip designer 
didn't worry too much about slew rate control, that's what they wanted 
to get rid of! :)

To "program" a different slew rate you need to set the Philips register 
to a sufficiently high $$$ value ;)

*Peter*

croquettegnu wrote:

> Hello Peter,
>
> I know what is a slew rate, do not worry about that and I had found
> this figures but I just wanted to know if the term __control__ in slew
> rate control extracted from the user manual signified that there is a
> way to change it
> Because as you probably know, changing this value could be very
> interesting regarding CEM...