Forums

Clocking question

Started by Brian Schmalz November 12, 2010
I'm a little green with LPC2000 parts - when a 'blank' part comes out of reset, should the crystal oscillator start running right away? I'm having the darnest time getting ISP to work, and I just probed the crystal and I don't see _anything_ happening on either leg.

Thanks-

*Brian

An Engineer's Guide to the LPC2100 Series

Hi Brian,

Read the User Manual first, specially the 'Boot / Flash Programming' and 'Clock'
sections.

In short, no..The main osc (xtal osc) won't be activated by default. It takes
user firmware to activate it. The internal RC will be activated by default.

Regards,
-daniel

________________________________
From: Brian Schmalz
To: "l..."
Sent: Fri, November 12, 2010 11:50:57 PM
Subject: [lpc2000] Clocking question

I'm a little green with LPC2000 parts - when a 'blank' part comes out of reset,
should the crystal oscillator start running right away? I'm having the darnest
time getting ISP to work, and I just probed the crystal and I don't see
_anything_ happening on either leg.

Thanks-

*Brian
Hi Brian,

Brian Schmalz wrote:
> I'm a little green with LPC2000 parts - when a 'blank' part comes
> out of reset, should the crystal oscillator start running right
> away? I'm having the darnest time getting ISP to work, and I just
> probed the crystal and I don't see _anything_ happening on either leg.

Which particular part are you working with? For example, the LPC2148
requires the crystal (or an external clock if in slave mode) to be
running before the internal reset circuit allows the CPU to start
(see section 10, chapter 4).

Also, what type of scope probe are you using to look at the pins? I
hope a x10 at the very least.

Cheers,
Neil
--
http://www.njohnson.co.uk

LPC2000 group:

Thanks for the suggestions and questions. It is a LPC2101 part. It turns out that the board I have had the crystal installed backward (it used a four pin SMT crystal where rotating 180 degrees grounds both sides of the crystal). Spinning it around got everything working perfectly.

*Brian

-----Original Message-----
From: l... [mailto:l...]On Behalf Of Neil Johnson
Sent: Monday, November 15, 2010 4:27 PM
To: l...
Subject: Re: [lpc2000] Clocking question

Hi Brian,

Brian Schmalz wrote:
> I'm a little green with LPC2000 parts - when a 'blank' part comes
> out of reset, should the crystal oscillator start running right
> away? I'm having the darnest time getting ISP to work, and I just
> probed the crystal and I don't see _anything_ happening on either leg.

Which particular part are you working with? For example, the LPC2148
requires the crystal (or an external clock if in slave mode) to be
running before the internal reset circuit allows the CPU to start
(see section 10, chapter 4).

Also, what type of scope probe are you using to look at the pins? I
hope a x10 at the very least.

Cheers,
Neil
--
http://www.njohnson.co.uk
lol
Charles AE5EW

--- In l..., Brian Schmalz wrote:
>
> LPC2000 group:
>
> Thanks for the suggestions and questions. It is a LPC2101 part. It turns out that the board I have had the crystal installed backward (it used a four pin SMT crystal where rotating 180 degrees grounds both sides of the crystal). Spinning it around got everything working perfectly.
>
> *Brian
>
> -----Original Message-----
> From: l... [mailto:l...]On Behalf Of Neil Johnson
> Sent: Monday, November 15, 2010 4:27 PM
> To: l...
> Subject: Re: [lpc2000] Clocking question
> Hi Brian,
>
> Brian Schmalz wrote:
> > I'm a little green with LPC2000 parts - when a 'blank' part comes
> > out of reset, should the crystal oscillator start running right
> > away? I'm having the darnest time getting ISP to work, and I just
> > probed the crystal and I don't see _anything_ happening on either leg.
>
> Which particular part are you working with? For example, the LPC2148
> requires the crystal (or an external clock if in slave mode) to be
> running before the internal reset circuit allows the CPU to start
> (see section 10, chapter 4).
>
> Also, what type of scope probe are you using to look at the pins? I
> hope a x10 at the very least.
>
> Cheers,
> Neil
> --
> http://www.njohnson.co.uk
>