Hi
I am trying to verify that my LPC2129 is running at 60MHz. I am
simply using the IOPIN command to toggle a GPIO pin.However the pin
stays high for 100ns not the expected 16.666ns.
I have set the VPDIV setting to 0x01; therefore PCLK is running at
the same frequency as the CCLK, and the mul and div settings are
correct to multiply up to 60M from an Oscillator of 20M
I have noticed when running the code that the VPBDIV setting chages
to 0x00; which sets the PCLK to 1/4 of the CCLK speed and then back
to 0x01.
Does anyone know why this happens.
I am using the startup.s file from the blinky examble in the Keil
Micro vision package.
Thanks
Scott
VPBDIV Setting Changes
Started by ●July 3, 2006
Reply by ●July 3, 20062006-07-03
Hello,
You can't toggle GPIO pins at the full processor frequency. A store operation
on an ARM7 core takes at least two cycles, but access to port pins requires
some additional cycles because the GPIO system is connected to a slower bus.
The newer LPCs like LPC214x have a fast-gpio feature allowing you to toggle
pins at 1/4th of the processor frequency (2 cycles per write access).
Regards,
Dominic Rath
On Monday 03 July 2006 13:53, scottkelsall wrote:
> Hi
>
> I am trying to verify that my LPC2129 is running at 60MHz. I am
> simply using the IOPIN command to toggle a GPIO pin.However the pin
> stays high for 100ns not the expected 16.666ns.
>
> I have set the VPDIV setting to 0x01; therefore PCLK is running at
> the same frequency as the CCLK, and the mul and div settings are
> correct to multiply up to 60M from an Oscillator of 20M
>
> I have noticed when running the code that the VPBDIV setting chages
> to 0x00; which sets the PCLK to 1/4 of the CCLK speed and then back
> to 0x01.
>
> Does anyone know why this happens.
>
> I am using the startup.s file from the blinky examble in the Keil
> Micro vision package.
>
> Thanks
>
> Scott
You can't toggle GPIO pins at the full processor frequency. A store operation
on an ARM7 core takes at least two cycles, but access to port pins requires
some additional cycles because the GPIO system is connected to a slower bus.
The newer LPCs like LPC214x have a fast-gpio feature allowing you to toggle
pins at 1/4th of the processor frequency (2 cycles per write access).
Regards,
Dominic Rath
On Monday 03 July 2006 13:53, scottkelsall wrote:
> Hi
>
> I am trying to verify that my LPC2129 is running at 60MHz. I am
> simply using the IOPIN command to toggle a GPIO pin.However the pin
> stays high for 100ns not the expected 16.666ns.
>
> I have set the VPDIV setting to 0x01; therefore PCLK is running at
> the same frequency as the CCLK, and the mul and div settings are
> correct to multiply up to 60M from an Oscillator of 20M
>
> I have noticed when running the code that the VPBDIV setting chages
> to 0x00; which sets the PCLK to 1/4 of the CCLK speed and then back
> to 0x01.
>
> Does anyone know why this happens.
>
> I am using the startup.s file from the blinky examble in the Keil
> Micro vision package.
>
> Thanks
>
> Scott
Reply by ●July 3, 20062006-07-03
Hi
Thanks for that
Kind Regards
Scott
--- In l..., Dominic Rath
wrote:
>
> Hello,
>
> You can't toggle GPIO pins at the full processor frequency. A
store operation
> on an ARM7 core takes at least two cycles, but access to port pins
requires
> some additional cycles because the GPIO system is connected to a
slower bus.
> The newer LPCs like LPC214x have a fast-gpio feature allowing you
to toggle
> pins at 1/4th of the processor frequency (2 cycles per write
access).
>
> Regards,
>
> Dominic Rath
>
> On Monday 03 July 2006 13:53, scottkelsall wrote:
> > Hi
> >
> > I am trying to verify that my LPC2129 is running at 60MHz. I am
> > simply using the IOPIN command to toggle a GPIO pin.However the
pin
> > stays high for 100ns not the expected 16.666ns.
> >
> > I have set the VPDIV setting to 0x01; therefore PCLK is running
at
> > the same frequency as the CCLK, and the mul and div settings are
> > correct to multiply up to 60M from an Oscillator of 20M
> >
> > I have noticed when running the code that the VPBDIV setting
chages
> > to 0x00; which sets the PCLK to 1/4 of the CCLK speed and then
back
> > to 0x01.
> >
> > Does anyone know why this happens.
> >
> > I am using the startup.s file from the blinky examble in the Keil
> > Micro vision package.
> >
> > Thanks
> >
> > Scott
>
Thanks for that
Kind Regards
Scott
--- In l..., Dominic Rath
wrote:
>
> Hello,
>
> You can't toggle GPIO pins at the full processor frequency. A
store operation
> on an ARM7 core takes at least two cycles, but access to port pins
requires
> some additional cycles because the GPIO system is connected to a
slower bus.
> The newer LPCs like LPC214x have a fast-gpio feature allowing you
to toggle
> pins at 1/4th of the processor frequency (2 cycles per write
access).
>
> Regards,
>
> Dominic Rath
>
> On Monday 03 July 2006 13:53, scottkelsall wrote:
> > Hi
> >
> > I am trying to verify that my LPC2129 is running at 60MHz. I am
> > simply using the IOPIN command to toggle a GPIO pin.However the
pin
> > stays high for 100ns not the expected 16.666ns.
> >
> > I have set the VPDIV setting to 0x01; therefore PCLK is running
at
> > the same frequency as the CCLK, and the mul and div settings are
> > correct to multiply up to 60M from an Oscillator of 20M
> >
> > I have noticed when running the code that the VPBDIV setting
chages
> > to 0x00; which sets the PCLK to 1/4 of the CCLK speed and then
back
> > to 0x01.
> >
> > Does anyone know why this happens.
> >
> > I am using the startup.s file from the blinky examble in the Keil
> > Micro vision package.
> >
> > Thanks
> >
> > Scott
>
Reply by ●July 3, 20062006-07-03
There's also a number of Errata that relate to VPDIV for the 2129 (use
of
EINT etc) so you may also wish to look there...
Andy
-----Original Message-----
From: l... [mailto:l...]On Behalf
Of Dominic Rath
Sent: 03 July 2006 13:05
To: l...
Subject: Re: [lpc2000] VPBDIV Setting Changes
Hello,
You can't toggle GPIO pins at the full processor frequency. A store
operation
on an ARM7 core takes at least two cycles, but access to port pins requires
some additional cycles because the GPIO system is connected to a slower bus.
The newer LPCs like LPC214x have a fast-gpio feature allowing you to toggle
pins at 1/4th of the processor frequency (2 cycles per write access).
Regards,
Dominic Rath
On Monday 03 July 2006 13:53, scottkelsall wrote:
> Hi
>
> I am trying to verify that my LPC2129 is running at 60MHz. I am
> simply using the IOPIN command to toggle a GPIO pin.However the pin
> stays high for 100ns not the expected 16.666ns.
>
> I have set the VPDIV setting to 0x01; therefore PCLK is running at
> the same frequency as the CCLK, and the mul and div settings are
> correct to multiply up to 60M from an Oscillator of 20M
>
> I have noticed when running the code that the VPBDIV setting chages
> to 0x00; which sets the PCLK to 1/4 of the CCLK speed and then back
> to 0x01.
>
> Does anyone know why this happens.
>
> I am using the startup.s file from the blinky examble in the Keil
> Micro vision package.
>
> Thanks
>
> Scott
EINT etc) so you may also wish to look there...
Andy
-----Original Message-----
From: l... [mailto:l...]On Behalf
Of Dominic Rath
Sent: 03 July 2006 13:05
To: l...
Subject: Re: [lpc2000] VPBDIV Setting Changes
Hello,
You can't toggle GPIO pins at the full processor frequency. A store
operation
on an ARM7 core takes at least two cycles, but access to port pins requires
some additional cycles because the GPIO system is connected to a slower bus.
The newer LPCs like LPC214x have a fast-gpio feature allowing you to toggle
pins at 1/4th of the processor frequency (2 cycles per write access).
Regards,
Dominic Rath
On Monday 03 July 2006 13:53, scottkelsall wrote:
> Hi
>
> I am trying to verify that my LPC2129 is running at 60MHz. I am
> simply using the IOPIN command to toggle a GPIO pin.However the pin
> stays high for 100ns not the expected 16.666ns.
>
> I have set the VPDIV setting to 0x01; therefore PCLK is running at
> the same frequency as the CCLK, and the mul and div settings are
> correct to multiply up to 60M from an Oscillator of 20M
>
> I have noticed when running the code that the VPBDIV setting chages
> to 0x00; which sets the PCLK to 1/4 of the CCLK speed and then back
> to 0x01.
>
> Does anyone know why this happens.
>
> I am using the startup.s file from the blinky examble in the Keil
> Micro vision package.
>
> Thanks
>
> Scott
