Reconfiguring LPC932 from High speed Oscillator option to Internal RC oscillator

[zaki]

hi,
   I am working on the MCB900 evaluation kit, and had changed the configuration of UCFG1 for the external oscillator and now want to reconfigure back to internal RC, however when i try to do that it says unable to connect, I had set the external oscillator same as the internal 7.373 MHz.
   Please help me out with this problem.
 zaki

[Andy Ayre]

Did you add an external crystal AND the trimming caps to the board? If not then you will need to add them before you can use the device again. It won't work without a crystal...

[zaki]

Andy,
   will u let me know the steps to perform to do this,
    thanks,
zaki

[Andy Ayre]

Solder a crystal into space Q1 next to the PLCC socket. Solders the caps into spaces C8 and C9, next to the crystal.

The Keil help file (included with the board but also linked to on the Flash Magic web page) contains the schematic diagram for the board.

[zaki]

   well in my project i want to vary the oscillator frequency and hence I am giving the clock to the P3.1 and the VSS on the TSSOP Pin Package. Prior to this I made the port 3 as quasi bidirectional. Let me know if I have to do anything else.
 Thanks,
     zaki

[Andy Ayre]

You said you configured the device for an external oscillator. If this is correct then you must attach a crystal. If you configured the device for an external clock input on XTAL1, then you can apply a clock signal to P3.1. The clock signal must be in the range 0 - 12MHz.

If you made all pins on Port 3 quasi-bidirectional, then that setting will be lost on the next reset. If you have the device configured to use an external clock on P3.1 then the device should configure the pin for you. I'm not sure what effect it will have if your executing code reconfigures the pin.

VSS must be at 0V - you cannot apply a clock signal to it.