Lpc2000

Hi,

I am using an LPC2129. My VPBDIV is set to '1'. I have been using 
EINT2 without a problem. I am able to set EXTPOLAR and EXTMODE 
without a problem. I am aware of the known errata about VPBDIV and 
EXTPOLAR so I set EXTPOLAR like this:

SCB_VPBDIV = 0 // first you set VPBDIV to 0
SCB_EXTPOLAR = 0x4;  // then set your EXTPOLAR bit
SCB_VPBDIV = 1;   // now, set VPBDIV back to what it originally was

Life is good when I do this. The problem is when I want to use EINT0 
and when I set EXTPOLAR for EINT0 to 1 my system appears to hang and 
I get no more serial port output. I set EXTPOLAR for EINT0 like this:

SCB_VPBDIV = 0
SCB_EXTPOLAR = 0x1;
SCB_VPBDIV = 1;

.. but when I run my code I lock up. I can set EXTPOLAR to 0x2, 0x4, 
or 0x8 but NOT 0x1. If I comment out these lines my code will 
continue.

Can someone help me with this? Am I not doing this correctly? Please 
help me set EXTPOLAR to 1 for EINT0 when I have a VPBDIV of 1.

Thanks,
Todd

Hi Todd,

> I am using an LPC2129. My VPBDIV is set to '1'. I have been using
> EINT2 without a problem. I am able to set EXTPOLAR and EXTMODE
> without a problem. I am aware of the known errata about VPBDIV and
> EXTPOLAR so I set EXTPOLAR like this:
>
> SCB_VPBDIV = 0 // first you set VPBDIV to 0
> SCB_EXTPOLAR = 0x4;  // then set your EXTPOLAR bit
> SCB_VPBDIV = 1;   // now, set VPBDIV back to what it originally was
>
> Life is good when I do this. The problem is when I want to use EINT0
> and when I set EXTPOLAR for EINT0 to 1 my system appears to hang and
> I get no more serial port output. I set EXTPOLAR for EINT0 like this:
>
> SCB_VPBDIV = 0
> SCB_EXTPOLAR = 0x1;
> SCB_VPBDIV = 1;
>
> .. but when I run my code I lock up. I can set EXTPOLAR to 0x2, 0x4,
> or 0x8 but NOT 0x1. If I comment out these lines my code will
> continue.
>
> Can someone help me with this? Am I not doing this correctly? Please
> help me set EXTPOLAR to 1 for EINT0 when I have a VPBDIV of 1.
>
> Thanks,
> Todd

I have played a little around with this and I have found that if you write
an extra 0 to _VPBDIV before you set the final _VPBDIV it will survive.

SCB_VPBDIV   = 0x00;
SCB_EXTPOLAR = 0x01;
SCB_VPBDIV   = 0x01;
SCB_VPBDIV   = 0x00   (extra write)
SCB_VPBDIV   = 0x01   (you final VPBDIV setting)

I think that the errate sheet assumes something like this in the code
sample.
But if you look at the code below (sorry folks, it's FORTH) that little \ufffd
just before the ok indicates that something strange happened on the serial
interface. I have the feeling that an interupt on the wrong place would be
bad.

0 vpb_div c! 1 ext_polar c! 1 vpb_div c! 0 vpb_div c! 1 vpb_div c!\ufffd ok

Regards
Kell