Lpc2000

This is my first ARM project so please excuse me if this is a dumb 
question.
I have an application where I need maximum GPIO speed.  The 
datasheet mentions that a VPB divider greater than 1 is needed at 
max processor clock speeds but I cannot find what that speed is.
What is the max clock speed for the VPB (GPIO) bus?

TIA

At 08:42 PM 10/6/04 +0000, you wrote:
>This is my first ARM project so please excuse me if this is a dumb
>question.
>I have an application where I need maximum GPIO speed.  The
>datasheet mentions that a VPB divider greater than 1 is needed at
>max processor clock speeds but I cannot find what that speed is.
>What is the max clock speed for the VPB (GPIO) bus?

Not a dumb question, it's not documented anywhere (at least I've not seen 
it).  A VPB of 1 appears to work with no problem up to 60MHz.  I suspect 
that the VPB is in there primarily for two reasons right now, 1- by 
reducing the peripheral clock speed you can reduce the power consumption of 
the peripherals and 2- if/when they go to a higher max speed they can 
document a lower max for the VPB and the HW already exists.  There is an 
interesting note in the RTC section that talks about higher envisioned bus 
speeds.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,
be they legal, genetic, or physical.  If you don't believe me, try to
chew a radio signal. "

                         Kelvin Throop, III

hi, yes correct. 60mhz is the max at the minute
if u are just getting started tehre is a pll calculator program in 
the Files section of this group which may be of assistance for you 
to see the possible clock speeds and various divider settings needed.

With regard to faster core speeds then I was talking to a guy from 
philips a couple of weeks ago and it was hinted that faster cores 
will be available in the future as teh current architecture should 
work up to around 80mhz...i may be off here, but that was my 
understanding at the time...

however the current hardware is limited to 60mhz.

one of the reasons for the VPBDiv is that in the future with a 
faster core clock, the Peripherals (eg RTC, UART, etc etc) that run 
of the VPB bus may not be able to run at the full core speed. At 
present however they are capable to run at the maximum clock speed 
of 60mhz.

as robert says reducing teh vpb speed will lower power consumption. 
u could obviously also look at powering down the peripherals u dont 
need if u are only concerned with the GPIO and still maintaining the 
60mhz clock.

hope this helps

rgds
pete


--- In lpc2000@yahoogroups.com, Robert Adsett <subscriptions@a...> 
wrote:
> At 08:42 PM 10/6/04 +0000, you wrote:
> >This is my first ARM project so please excuse me if this is a dumb
> >question.
> >I have an application where I need maximum GPIO speed.  The
> >datasheet mentions that a VPB divider greater than 1 is needed at
> >max processor clock speeds but I cannot find what that speed is.
> >What is the max clock speed for the VPB (GPIO) bus?
> 
> Not a dumb question, it's not documented anywhere (at least I've 
not seen 
> it).  A VPB of 1 appears to work with no problem up to 60MHz.  I 
suspect 
> that the VPB is in there primarily for two reasons right now, 1- 
by 
> reducing the peripheral clock speed you can reduce the power 
consumption of 
> the peripherals and 2- if/when they go to a higher max speed they 
can 
> document a lower max for the VPB and the HW already exists.  There 
is an 
> interesting note in the RTC section that talks about higher 
envisioned bus 
> speeds.
> 
> Robert
> 
> " 'Freedom' has no meaning of itself.  There are always 
restrictions,
> be they legal, genetic, or physical.  If you don't believe me, try 
to

> chew a radio signal. "
> 
>                          Kelvin Throop, III

At 08:56 PM 10/6/04 +0000, you wrote:
>as robert says reducing teh vpb speed will lower power consumption.
>u could obviously also look at powering down the peripherals u dont
>need if u are only concerned with the GPIO and still maintaining the
>60mhz clock.
Also take a look at the discussions we had earlier in this group on GPIO 
speed if that's critical for you.  It will be in the first month or two of 
the archives.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,
be they legal, genetic, or physical.  If you don't believe me, try to
chew a radio signal. "

                         Kelvin Throop, III

Hello

For the record:
The assumptions about VPB divider being there to lower power, prepare
for faster core speeds are all correct.
Also the statement that existing peripherals run at full speed of VPB
is correct.

Regards, Robert


--- In lpc2000@yahoogroups.com, Robert Adsett <subscriptions@a...> wrote:
> At 08:56 PM 10/6/04 +0000, you wrote:
> >as robert says reducing teh vpb speed will lower power consumption.
> >u could obviously also look at powering down the peripherals u dont
> >need if u are only concerned with the GPIO and still maintaining the
> >60mhz clock.
> Also take a look at the discussions we had earlier in this group on
GPIO 
> speed if that's critical for you.  It will be in the first month or
two of 

> the archives.
> 
> Robert
> 
> " 'Freedom' has no meaning of itself.  There are always restrictions,
> be they legal, genetic, or physical.  If you don't believe me, try to
> chew a radio signal. "
> 
>                          Kelvin Throop, III