Lpc2000

Hi Dave B

Why do you use 12.288MHz clock? Do you connect audio codec to LPC2131?

d> Hi Marcio,
d> Yes, that mode of operation is supported.  I have been running a 
d> LPC2131 with an external 12.288MHz clock that is buffered and feeds 
d> everything on my board.  Works fine.

d> See page 31/32 of the manual.  There is some info there although I 
d> agree it is not very clear.  Just leave the unused pin 61 (XTAL2) 
d> open.  Also, make sure you use the recommended (100pF) coupling cap 
d> for XTAL1.
d> See figure 7a for slave mode.

d> Good Luck,
d> Dave B.

Hi all,
   If I put an external clock on XTAL1 input (instead of quartz
crystal) everything will run ok ? I can�t find the answer on datasheet.
Thanks,
          Marcio

Hi Marcio,
Yes, that mode of operation is supported.  I have been running a 
LPC2131 with an external 12.288MHz clock that is buffered and feeds 
everything on my board.  Works fine.

See page 31/32 of the manual.  There is some info there although I 
agree it is not very clear.  Just leave the unused pin 61 (XTAL2) 
open.  Also, make sure you use the recommended (100pF) coupling cap 
for XTAL1.
See figure 7a for slave mode.

Good Luck,
Dave B.





--- In lpc2000@yahoogroups.com, "atmelbr" <atmelbr@y...> wrote:
>
> Hi all,
>    If I put an external clock on XTAL1 input (instead of quartz
> crystal) everything will run ok ? I can´t find the answer on 
datasheet.

> Thanks,
>           Marcio
>

Alex,
No, I do not connect the codec to the micro.  The primary function of 
my project is to pass audio.  And I do use a codec and a DSP.  

The codec must have a 12.288MHz clock to generate the bit and frame 
clocks for 24-bit 48kHz sampled audio.  Since I have to have this 
clock anyway, why not use it for the 2131 as well?  It saves me some 
money and works fine.  I am still able to use the UART for 
communications and I also use I2C, SPI, PWM without a problem at this 
frequency (actually the PLL is set up for M=4 ==> 49.152MHz)

Dave

--- In lpc2000@yahoogroups.com, Alex_Rambler <bor-alex@r...> wrote:
>
> Hi Dave B
> 
> Why do you use 12.288MHz clock? Do you connect audio codec to 
LPC2131?
> 
> d> Hi Marcio,
> d> Yes, that mode of operation is supported.  I have been running a 
> d> LPC2131 with an external 12.288MHz clock that is buffered and 
feeds 
> d> everything on my board.  Works fine.
> 
> d> See page 31/32 of the manual.  There is some info there although 
I 
> d> agree it is not very clear.  Just leave the unused pin 61 
(XTAL2) 
> d> open.  Also, make sure you use the recommended (100pF) coupling 
cap 

> d> for XTAL1.
> d> See figure 7a for slave mode.
> 
> d> Good Luck,
> d> Dave B.
>

Hi, Dave B.
Is your external 12.28Mhz clock source working fine with the Lpc2xxx
internal clock multiplier?  Did you turn on Clock PLL on the LPC2131?
Thanks in Advance.

--- In lpc2000@yahoogroups.com, "drb5599" <dbutler@c...> wrote:
>
> Hi Marcio,
> Yes, that mode of operation is supported.  I have been running a 
> LPC2131 with an external 12.288MHz clock that is buffered and 
feeds 
> everything on my board.  Works fine.
> 
> See page 31/32 of the manual.  There is some info there although I 
> agree it is not very clear.  Just leave the unused pin 61 (XTAL2) 
> open.  Also, make sure you use the recommended (100pF) coupling 
cap 

> for XTAL1.
> See figure 7a for slave mode.
> 
> Good Luck,
> Dave B.
> 
> 
> 
> 
> 
> --- In lpc2000@yahoogroups.com, "atmelbr" <atmelbr@y...> wrote:
> >
> > Hi all,
> >    If I put an external clock on XTAL1 input (instead of quartz
> > crystal) everything will run ok ? I can´t find the answer on 
> datasheet.
> > Thanks,
> >           Marcio
> >
>

Marcio,
I have not had any problems with the PLL.  I set it up for M=4, P=2 (just follow the equations in the manual to come up with your own values).  So the processor clock (cclk) is 12.288MHz * 4 = 49.152MHz.  This frequency is plenty fast for what I am doing.  Yes, it is not a pretty whole number frequency, but that is not important for this application.  FYI, I am also using the UART0, SPI, I2C and PWM.
Good Luck,
Dave B.

-----Original Message-----
From: unity0724 [mailto:unity0724@...]
Sent: Friday, November 11, 2005 8:48 AM
To: lpc2000@yahoogroups.com
Subject: [lpc2000] Re: External clock on LPC2131


Hi, Dave B.
Is your external 12.28Mhz clock source working fine with the Lpc2xxx
internal clock multiplier?  Did you turn on Clock PLL on the LPC2131?
Thanks in Advance.

--- In lpc2000@yahoogroups.com, "drb5599" <dbutler@c...> wrote:
>
> Hi Marcio,
> Yes, that mode of operation is supported.  I have been running a 
> LPC2131 with an external 12.288MHz clock that is buffered and 
feeds 
> everything on my board.  Works fine.
> 
> See page 31/32 of the manual.  There is some info there although I 
> agree it is not very clear.  Just leave the unused pin 61 (XTAL2) 
> open.  Also, make sure you use the recommended (100pF) coupling 
cap 
> for XTAL1.
> See figure 7a for slave mode.
> 
> Good Luck,
> Dave B.
> 
> 
> 
> 
> 
> --- In lpc2000@yahoogroups.com, "atmelbr" <atmelbr@y...> wrote:
> >
> > Hi all,
> >    If I put an external clock on XTAL1 input (instead of quartz
> > crystal) everything will run ok ? I can´t find the answer on 
> datasheet.
> > Thanks,
> >           Marcio
> >
>







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